Reload CUDA driver?

Hi,
For some reason, after rebooting my Linux system (redhat 5.4), the CUDA driver can no longer find the device. I am wondering if there is anyway to reload CUDA driver instead of reinstall it? Or is there anyone having a similar issue? Thanks!
Yu

Are you running X11 or have you done a kernel upgrade recently?

Yes, the X server is on, but not sure if the kernel being updated because the reboot was due to machine crash.

Thanks!

sudo restart gdm

Also useful is:
sudo stop gdm
sudo start gdm

those two can be used to stop X11 usually so you can edit your xorg.conf or install a new driver, then start X again.