Angry US MacBook owners may launch a class action suit against Apple regarding a fault in some machines that causes intermittent shut downs of the computers.

Reports have circulated since the MacBooks launched that, after a period of normal use, the computers will shut down at random moments.

These shut downs are irregular - a user can enjoy their machines freely for an indeterminate period, but the machines may still shut down, seemingly at random.

Apple recently told its authorised Mac repairers to replace the heat sink in affected models first. If that doesn't fix the problem, then the company is replacing logic boards in affected machines. The problem led to a temporary supply shortage of logic boards.

Apple in August released the MacBook SMC Firmware Update, which adjusted fan behaviour in these machines, and helped lower running temperatures.

Mac OS X 10.4.8 is also meant to help ease the problem.

Apple's customer service teams are asking users who contact them regarding the problem to "re-seat" any installed RAM.

The company's damage control measures have left some MacBook owners without use of their machines for weeks, according to the MacBook Random Shutdown website, which has registered 1,394 instances of the problem.

Understandably frustrated at long queues at the Genius Bar, and extended periods without their brand-new Mac, some owners are now filing their names on a website that collects names and other information for potential class action lawsuits.

Meanwhile, it appears that Apple has geared-up its support teams to grapple with this issue, and has ensured a supply of the relevant spare parts to repair the problem (heat sink and logic board). Insiders told Macworld that the diagnosis and repair of this fault can now be accomplished within two hours at an Apple Store.

Apple hasn't yet introduced a priority scheme for affected MacBook owners in order that they don't have to endure the long waits for service at a Genius Bar.