I have a MBP (late '08) and have had the same issues as others here, a complete freeze with no response from keyboard or mouse, and also issues with the Airport card not being recognized. Extended hardware test, nothing. Reinstall Leopard and Snow Leopard, nothing. Did all available updates, nothing.
I took it into the Apple store, and they said it could be a problem with the Airport card since it sits on the logic board. They said they would replace it. A day later, they said they could not replicate the problem and did not do anything to the computer.
I took it home, and had the same problems with it that I was having before. I upgraded to 10.6.2. Same problems. I did notice that the freezes occurred if I moved, bumped, or tilted the MBP while it was running, making me think something inside was loose. A relative of mine is an IT professional and opened it up but not being too familiar with Macs couldn't do much. He retightened all the screws and things he could find, and since then it worked fairly well, until a day ago and the problems started all over again.
I love the Macs, but this is extremely frustrating! If anyone has any solutions, I would appreciate it.