Did you run the installer in failsafe mode?
If so, don't do that.
Oh, and then do the following.
But even if that's not how you installed it, the following should still fix it for you:
Add a line to /etc/modules.conf reading alias /dev/nvidia* nvidia
, save and exit, and run /sbin/depmod -ae
Next time you reboot, the error shouldn't come back.