InformationWeek reports that a third-party MacBook power adapter manufacturer is being sued by Apple for allegedly violating one of its patent designs.

On Monday, Apple filed a patent infringement lawsuit against Media Solutions Holdings in federal district court in California. Apple says that the company is using various different websites and business entities to sell what they describe as a ‘knock-off’ MacBook power adapter. “Through various Web sites and otherwise,” Apple says in the suit, “…the Defendants market these knock-off power adapters for use with Apple portable computers, such as the MacBook.”

The websites include laptopsforless.com, laptopacadapter.com and ereplacements.com. Apple says these sites sell “various consumer electronic accessories at retail,” and the naughty power adapter is amongst the products they sell.

The other named defendents also include companies eReplacements and Laptops For Less.

Apple also adds in the claim that, “The Defendants’ infringing conduct has damaged Apple and inflicted irreparable harm.” They don’t elaborate on the monetary value of that “harm” but they do seek an injunction against the defendants that stops them selling their knock-off adapters. For now, the offending power adapters have been removed from sale from the websites listed in the suit (but although they can no longer be ordered, they are still listed on those sites).

The suit includes line-drawing illustrations comparing designs from Apple’s power adapter patent with photographs of the power adapter sold by the defendants. The patent was awarded to Apple by the United States Patents and Trademarks Office over six years ago, in August 2003.

InformationWeek notes that Apple is not accustomed to being the Plaintiff in patent disputes; of the 15 patent lawsuits filed during the second half of this year, Apple has been the defendant in every case but this one. At an average litigation cost of $4.5 million (through trial), that’s a tremendous expense created — for the most part — by what InformationWeek calls “non-practicing entities” but what the rest of us call Patent Trolls.

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A lot of people definitely did though, because in 2001 Apple recalled about 570,000 of those suckers. I remember when Apple first gave the announcement about the faulty adapters and I picked a replacement up for free just in case (and because, well, it was free).

If you’re one of those lucky few to experience some extra heat on your lap, you may be entitled to a refund. If your adapter “dangerously frays, sparks and prematurely fails to work” Apple has agreed to throw you $25 to $79 for your troubles.

This class-action suit was actually way back in 2006 and alleged that Apple misrepresented problems with the power adapters. I can’t help but think most people have moved on from their old PowerBook immolation issues by now.

Related research and analysis from GigaOM Pro:
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• Why iPad 2 Will Lead Consumers Into the Post-PC Era
• The Near-Term Evolution of Social Commerce
• Content Farms: The Players, The Benefits, The Risks