I have an nvidia card and am running Ubuntu 8.10. I also have this bug.
What I've found though is that the screen renders white -but my system
doesn't crash. In fact, if I enter my password, I log back into my
account and everything is totally fine: no rendering problems, no
functionality issues.
Just thought I'd add this:
I just tried locking my screen as User1. The screen-saver started
running. I hit ESC to exit the screen-saver and log back in. I was
prompted with the standard unlock login prompt (no white screen).
At this screen I chose Switch User instead of logging in. I was
I can confirm this within Firefox (Mozilla/5.0 (X11; U; Linux x86_64; en-US;
rv:1.8.1.11) Gecko/20071204 Ubuntu/7.10 (gutsy) Firefox/2.0.0.11), but not in
gEdit.
I've testing this in several situations (save page as, save download, open
file, save frame as). The two features that repeat the bug
