make sure the required alias is in the modules.conf file and make sure you have PNP OS Aware disabled in bios (or whatever yours is called) and make sure you have assign irq to vga set to enabled in bios....
/****DO THIS IF NONE OF THE ABOVE FAIL TO WORK*****/
post any relevant errors that you see in the /var/log/xfree86.0.log file when USING the nvidia driver...
the beginning of the lines will say something like
if you see something like:
(II) NV(0), then don't post it, make sure it says the nvidia one...
boot to init 3, change driver to nvidia, then type startx, watch it crash and reboot...boot back to init 3, and before making any changes, make a copy of the /var/log/xfree86.0.log file with the output from the nvidia driver, then change back to the nv driver and post the relevant errors in that log file.