Comment 3 for bug 726268

I'm experiencing similar symptoms with a partially same setup.
Nvidia 9600GS with current (270) driver. xorg process starts out about 200M but steadily climps and after a day or 2 hits a gig. Unfortunately if I then run out of memory, xorg is targetted by the kernel for a kill and I lose my session.
Previous to 11.04, if i ran out of ram it would kill Firefox or some other application, and leave my session running. I can only assume that the reason for xorg being targeted is the amount of memory it is using (ideally the kernel should pop up a dialogue under memory limit conditions giving the opportunity to decide which app to kill... or at least know that x isn't a good choice).
Suffice it to say, this is a rather destructive bug. I don't much like losing work due to an X session ending.