I’ve got a refurb MacBook Pro that I love and use as my mobile machine. When I first got it, first thing I did was replace the standard memory with 2GB of non-apple memory. Apples prices at the time were too high (not so any more).
Worked perfectly for almost 10 months. Then after some 10.4 updates everything seemed to go downhill. Frequent and unexplained kernel panics. I lived with it for a while, tried to a narrow it down, in the end I decided to just reinstall after talking with AppleCare.
I picked the option that let me keep all my files, and after a reinstall I actually got all my data back. Was quite happy about that…. and no panics so far (crosses fingers).
So, if your getting kernel panics that seem recent and unexplained, consider an OS X reinstall.