I have encountered an oops while running Xfree 4.1.0 and doing everyday work (debugging a program with ddd). It resulted in a complete lockup (as it was X), but I could still login via ssh.
I do not know if the attached ksymoops output is of much help to you, I see that it references often to NVDriver, so maybe it is an nvidia problem, but as I am not sure I'm posting it here anyway.
Kernel: 2.4.17
Distro: Debian Sid
Gcc: 2.95.4
modutils: 2.4.12