I have a linux desktop at work that, until 2 days ago, was completely stable. 200+ days of uptime and no problems at all. Running ubuntu 10.04, if memory serves. I mostly use it for piddly perl stuff and administering a website via ssh.

All of a sudden, it locked up and I had to restart. Ever since, the system will only stay up for a few hours at most. Often, the display goes weird with strange blocking and tearing, while I can still kind-of use the gui. The system will do weird things, like the GUI will work, but I can't launch any programs...even simple things like nautilus. Sometimes the simplest programs like top and du instantly die saying 'killed'. Or they start but then segfault. One time I switched to a virtual terminal to try to restart the xserver, but I couldn't log in...when I entered my credentials I got a screen of debug information including weird memory addresses and a message saying BUG: unable to handle kernel paging request. Since I can't log in, I had to power-cycle. Or the system just locks up hard.

I ran 3 passes of memtest this morning and no errors.

Are there any log files I can look at that might tell me what's wrong? I can try a clean reinstall, but my home directory is encrypted and I'm worried that re-mounting it to a new install might be interesting.

You could look at /var/log/Xorg.0.log, /var/log/messages, and /var/log/syslog for starts.

You could also try starting one of the recalcitrant programs, such as nautilus, from the command line and capturing the error messages, if any. That might tell you more than the logs. If the box is locking up hard, you might want to have a digital camera handy so you can take a picture of the screen.

Good luck.