I'm attempting to track down a problem with a friend's 14" iBook G4/933; the computer will freeze after several (not more than 10) minutes of use. I tried all the usual stuff (reset PRAM, ran with DIMM removed, booted from Panther install CD, ran fsck on the hard drive) with no results. The machine runs fine in single-user mode, including very CPU-intensive tasks like cat /dev/urandom > /dev/null I began to suspect the onboard RAM, but without a proper memory tester like Memtest+ for the Mac platform, I couldn't verify this. I wrote a crude memory tester of my own: a ruby script that allocates huge arrays, fills them with random numbers, then does math with the contents. I ran the script in single-user mode while watching with top. Doing this almost always freezes the computer with about 100M of RAM in use, which seemed to confirm my guess. I replaced the onboard RAM. This was a fairly difficult repair, but it appears to have worked; my script no longer freezes the machine in single-user mode. The problem is, the machine still freezes in normal use and while attempting archive/install from the Panther CD. I'm not sure what else to try with this machine. Ideas?

Is it still under warranty?