Here is the Apple Support discussion about it, and here is a great thread on macosxhints.com.
Long story short, here is the edited version of the kernal panic (aka huge catastrophic crash) log:
Thu Mar 8 22:40:18 2007
panic(cpu 0 caller 0x000A8800): Uncorrectable machine check:
Kernel loadable modules in backtrace (with dependencies):
See that? Airport with 405.1 driver. I have been using this comp with out airport on for over an hour and things are going great. So the fix? Well its an evolving situation with the discussion happening right now. Apple has not addressed the issue, but they are going to be sued about it soon for a fix.
There are two theories, first its a pure software issue with the interaction of the Airport and certain wireless base stations brought about by the 10.4.8 upgrade. That would be great because you can fix software really easy.
The second says that the card's connection is bad, and that opening up the computer and fixing that is the solution.