On Fedora 9 x86_64, any time a user logs onto an X session, the permissions on /dev/nvidiactl and /dev/nvidia0 are changed to R/W access for that user and no permissions for anyone else.
[jholewinski@cerberus ~]$ ls -l /dev/nvidiactl
crw------- 1 jholewinski root 195, 255 2009-07-15 13:37 /dev/nvidiactl
I can manually chmod the permissions to something reasonable, but the permissions are reset whenever a new X session is created. Since this is a multi-user system, it is becoming an annoyance. This is happening with the 185 CUDA 2.2 drivers, and the 177.80 drivers.