I'm having the same problem under Debian Wheezy (testing).
The problem is present with the 302.xx driver and it gets worse with the 304.xx series (Xsession fails and returns me to login screen - lightdm).
What is up with this? is NVIDIA looking at this issue at all? card is a GeForce 8300 GS. I'm currently using nouveau which is working much much better.
I cannot downgrade to other drivers because I'm using Xorg server 1.12.x
How do we submit bug reports to NVIDIA?
Here is a bug report in Debian, which has all the information I could gather:
I've also found another report of the same breakage on a 8400 gs card as well: