Comment 28 for bug 765136

There appears to be various reasons for X/GDM crashing. I got some "signal 3"s in the gdm logs, while others (in other bugs got crashes with signal 11). The old bug described in
https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/396226 was consistent with the behaviour I saw: logged out while typing, and if I then switched to tty1 (with Crtl-Alt-F1) it showed some garbled text. Disabling splash appears to have fixed it - did it yesterday, and no forced logouts today. For a discussion of the actual culprit, read the bug and comments.

Regarding my setup: I have two boxed upgraded to 11.04, and one fresh install. Only one of the updated boxes had the forced logout behaviour. All of the boxed had full disk encryption, but the one with problems also had an issue regarding the splash screen after entering passphrase: I had to jump out of the the splash screen, by pressing "Esc(ape)" at the latest right after entering the passphrase, otherwise the splash screen would lock up and I would have to reboot. Today, I could boot without any "security by obscurity" keypress magic (albeit text only boot) and I have not been kicked out of this session. I have done some other tweeks as well, but chaning between "Ubuntu Classic" and Unity made no difference. I don't know what I've done to trigger #396226, but I'm happy now, knowing that it was a software issue and not hardware as I suspected. Others might shed some light on why this issue reappearing on 11.04 (for some configurations).