I installed the original 10.2.8 updated and started getting crashing, freezing, kernel panics, and getting logged out when the window server crashed.
Downgraded to 10.2.6 and everything was fine.
Applied the new 10.2.8 update and was experiencing the same thing.
Tried everything including a clean install, but nothing worked until I removed the 512 meg chip that came with my 17" Powerbook.
Removing the Apple memory has made may machine stable again. I still have a 512 chip from Ramjet.com in my machine and it is running faster then it has every.
Tomorrow I'm calling Apple to see if they will replace the chip as the machine is less then 2 months old.