[Update: the stores are back up and sure enough, the iMac product line has been updated. Same prices, better specs. Apple press release here.]

Apple’s online stores were closed early Monday around the world, a pretty dependable sign that new products were about to be announced.

The most likely candidate: an upgraded iMac. Last week Geeksugar, a rumor site with a good track record, passed along word that Apple would soon be refreshing its line of desktop computers with bigger hard drives and faster (presumable Intel Penryn) processors. (link)

According to AppleInsider, a memo out of Cupertino gave some of Apple’s (AAPL) U.S. retail partners a heads-up on the new iMacs and that placeholders for the computers have appeared on BestBuy’s computers. (link)

The successor to the original 1998 Bondi-blue iMac G3, the current Intel (INTC) Core 2 Duo aluminum iMac was introduced Aug. 7 in two models, a 20″ and a 24″.

Apple usually announces new products on Tuesdays.

MacRumors has issued an update of its immensely useful Buyer’s Guide — a consumer-oriented cheat sheet that tracks the update cycle of Apple’s product line and offers informed opinions about whether you should go ahead buy that MacBook Pro you’ve been lusting after or wait for the next model. As MacRumors put it:

Apple updates their products in a very consistent manner. A Mac comes out at a certain price with certain features. The price and features of that particular Mac stay exactly the same throughout the lifespan of the product. So, if a customer buys on Day #1, they are getting the fastest/newest technology for the dollar. The problem, however, is that 8 months later, on the day prior to its refresh, that Mac costs the exact same money, but contains 8 month old technology. (link)

Although based on rumors and second-hand reports, the Guide is pretty dependable, especially since Apple (AAPL) switched to Intel chips. Intel (INTC) is quite open about its product plans, and Apple tends to switch to their newest processors in a fairly predictable timeframe. (Although as MacRumors notes, Intel’s switch to the Nehalem microarchitecture, due late this year, could stretch out some Apple product cycles.)

To see the full 2008-2009 Buyer’s Guide, click here. This is a summary of their recommendations:

• iPod classic: Buy only if you need it - Approaching the end of a cycle
• iPod touch: Neutral - Mid product cycle
• iPod nano: Buy only if you need it - Approaching the end of a cycle
• iPod shuffle: Buy - Product recently updated
• Mac mini: Don’t Buy - Updates soon
• Mac Pro: Neutral - Mid product cycle
• MacBook: Buy - Product recently updated
• MacBook Pro: Buy - Product recently updated
• iPhone: Buy only if you need it - Approaching the end of a cycle
• LCDs: Don’t Buy - Updates soon
• Xserve: Buy - Product recently updated

There’s lots more information in the full Buyer’s Guide, including historical release dates, days since update and links to recent news.

One caveat: you take a risk when you buy a computer on Day #1, as MacRumors suggests. You might want to monitor Apple’s discussion boards for few weeks to see what problems emerge. Let the company and the users who like to live on the bleeding edge work out the kinks before you buy.

Two complaints about Apple’s popular aluminum iMac line — the “washed out” look of the 20-inch iMac that surfaced on Apple’s discussion boards last summer (see here) and the “millions of colors” issue that was recently settled by the company — were rolled into one class-action lawsuit filed Monday in U.S. District Court in San Jose.

The plaintiff — a Texan named Chandra Sanders — claims to represent tens of thousands of customers who purchased the smaller of the two iMacs introduced last August. She is demanding a jury trial.

At the center of her complaint is the allegation that while 24-inch iMacs are capable of displaying 16,777,216 colors on 8-bit, in-plane switching (IPS) screens, the 20-inch iMac have 6-bit twisted nematic film (TN) LCD screens that can display only 262,144 colors.

Much of the 15-page complaint is taken up repeating statements made by Steve Jobs at the product introduction and by marketing messages issued later by Apple (AAPL) that describe the two displays as if they were interchangeable.

Apple’s website, for example, says that “No matter what you like to do on your computer — watch movies, edit photos, play games, even just view a screen saver — it’s going to look stunning on an iMac.”

In fact, say the plaintiff’s representatives, “the inferior technology of the 20-inch iMac is particularly ill-suited to editing photographs because of the display’s limited color potential and the distorting effect of the color simulation processes… Apple deceptively marketed its new 20-inch iMac in a way that grossly inflated the capabilities of its monitor, which is vastly inferior to the previous generation it replaced.”

“Apple is duping its customers into thinking they’re buying ‘new and improved’ when, in fact, they’re getting stuck with ‘new and inferior,’” said Brian Kabateck of Kabateck Brown Kellner, the Los Angeles firm that is handling case. “Beneath Apple’s ‘good guy’ image is a corporation that takes advantage of its customers. Our goal is to help those customers who were deceived and make sure Apple tells the truth in the future.”

Ms. Sanders claims to have lost “money or property” as a result of Apple’s “unfair, unlawful and fraudulent” actions, although no dollar figure is provide.

It its press release, Kabateck Brown Kellner LLD describes itself as “one of the nation’s foremost consumer law firms.” The firm claims that its clients have won more than $750 million against Google (GOOG), Farmer’s Insurance, Eli Lilly (LLY) and other major corporations.

A few bits of Apple (AAPL) news worth noting:

Paul McCartney: “It’s all happening soon,” he told Billboard.com. “Most of us are all sort of ready. The whole thing is primed, ready to go — there’s just maybe one little sticking point left, and I think it’s being cleared up as we speak, so it shouldn’t be too long. It’s down to fine-tuning. I’m pretty sure it’ll be happening next year, 2008.” (link)

“Let me put that statement into American English,” says Fake Steve Jobs. “Paul wants more money.”

First Leopard Update: More than a dozen improvements in Mac OS X 10.5.1, issued three weeks after Leopard’s release, including fixes in Mail, Airport, Time Machine, Back to My Mac and some pesky Firewall issues. Not yet repaired: Among the repairs: that nasty core data bug.

iMac Anti-freeze: Apple also released a graphics firmware update that’s supposed to finally solve the freezing problem some aluminum iMac users have been suffering since September. I’ll believe it when my Dad tells me his iMac has gone more than a week without crashing.

Three New Mac Ads: The Get-a-Mac ads are back on TV (and available from Apple here) after a summer hiatus. “Same joke,” writes Michael Gartenberg. “Still as effective.” But maybe not quite as funny.

This is a story about my father’s iMac. But it could be anybody’s dad, and any 20-inch Intel iMac equipped with ATI Radeon HD graphics cards.

At the end of August, my 85-year-old father ordered one of the new skinny iMacs. A few days after it arrived, I took a train to Boston and helped him transfer files from an ancient Mac running OS 9. It took most of a weekend, but by the time I left, everything was working fine.

On September 26, he sent this e-mail.

The Mac crashed. The pointer did not move. I restarted with the power button and it came up with a white bar pattern. I restarted with the pointer and apple and all was normal. — Dad

It was the first of long string of similar messages. His tale of woe — and Apple’s (AAPL) eventual response — continues below the fold.

In the days before Apple’s (AAPL) quarterly earnings report, several analysts hastily raised their estimates for the company’s Q4 profits — as if fearing a repeat of the last four quarters, when the company beat Wall Street’s targets by anywhere from 22% to 46%.

But it was too little too late. As CNNMoney reported at the close of market today, Apple posted sharply higher sales and earnings in the quarter that ended Sept. 29. With revenue of $6.22 billion and earnings of $1.01 cents per share, Apple blew past not only its target of 65 cents a share, but the analysts’ average estimate of 86 cents.

Analyst Shaw Wu of American Technology Research, who had predicted sales of $6.05 billion, proclaimed it an “all-around strong quarter.”

“Very impressive,” said Piper Jaffray’s Gene Munster. “Everything is just clipping along.”

What surprised both analysts the most, however, was Apple’s rosy prediction of a blowout Christmas quarter with sales of $9.2 billion and earnings of $1.41 a share — a sharp contrast to the company’s tradition of extremely cautious forward-looking guidance. “It’s the first time in three quarters they’ve given guidance higher than Wall Street’s,” says Munster. “This could push Street estimates up 25% to 30%.”

Apple’s shares closed at all-time record high of 174.36, up 2.31% for the day, and added another 12 points in after-market trading.

How did Steve Jobs & Co. do it?

In a word: Macintosh. The company sold 2.164 million Macs in the quarter, accounting for 62% of the company’s revenue. Sales were up 34% year to year and set a company record for the fall quarter, thanks in large part to back-to-school promotions.

Macintosh market shares are up sharply in Europe and even Japan, where sales have lagged, and Munster estimates that Apple’s worldwide market share could grow from 3% to 3.2% as a result of the Mac surge. Earlier estimates of Apple’s share of the U.S. computer market put it anywhere from 6.2% to 8.1%.

iPhone sales were also impressive — 1.12 million sold in the quarter, with a burst of sales after the September $200 price drop — but because Apple spreads its cellphone revenue across 24 months, the iPhone impact on Q4 earnings was less significant.

The one place where Apple failed to meet expectations was in iPod sales. The company reported 10.2 million iPods sold in the quarter — a shade fewer than the 10.9 million analysts were expecting.

But where it matters most — profitability — Apple continues to shine. Its gross margin for the quarter was 33.6%, up from 29.2% a year earlier. That’s not even in the same ballpark as Apple’s competitors in the cut-throat computer and cellphone industries.

Steve Jobs has clearly learned how to leverage his company’s advantage in design and ease of use to the benefit of Apple’s investors — and the company’s bottom line.

See Apple’s press release here.

For a transcript of the earnings call, click here.

For background, see Apple Earnings Preview: Firing on All Cylinders

In terms of relations with its users and business partners, the quarter that ended Sept. 30 wasn’t a particularly easy one for Apple (AAPL). There were complaints and lawsuits about the cost of replacing the iPhone’s battery, the surprise $200 price cut, and the software update that “bricked” untold numbers of unlocked phones. Negotiations with Hollywood and the European iPhone partners were awkward and protracted and in the case of NBC ended in an impasse. Consumers who bought the new entry-level skinny iMacs are still complaining about low-quality screens and an unresolved software glitch that’s causing random freezes.

But in terms of sales and profitability, the consensus among analysts is that the fiscal fourth quarter was a terrific quarter for Apple, buoyed by back-to-school specials, switchers fleeing Vista, and a flood of hot new products. The line on Apple heard most often on the Street — in a cliche borrowed from the automotive industry — is that Steve Jobs’ profit-generating machine is firing on all cylinders these days and will handily beat Apple’s guidance numbers (never particularly hard to do, given how conservative those numbers tend to be).

As the chart below the fold shows, the analysts who follow Apple most closely are marching pretty much in lockstep this quarter, with Cupertino’s guidance as the sole outlier. Everybody seems to be expecting the company to report sales of more than 2 million Macs, 10 million iPods and a million iPhones, give or take a few truckloads.

The biggest news, says PiperJaffray’s Gene Munster, is likely to be the disclosure for the first time of how much revenue Apple has been collecting — and amortizing over 24 months — from AT&T (T) for iPhone sales and monthly user fees. The precise terms of Apple’s revenue-sharing arrangements with cellular carriers here and abroad have been, until now, a closely held secret. Munster estimates that the AT&T deal could add $10.6 million to Apple’s bottom line in Q4 alone.

Apple will announce its quarterly earnings on Monday Oct. 22 after the market closes and meet by phone with reporters and analysts an hour later. Click here at 5 p.m. ET (2 p.m. PT) to listen in on Apple’s webcast. Fortune’s analysis of the results will be posted here.

Below, as promised, is a sampling of Q4 estimates: