In fact I do have some suggestions
first of all make sure your X server configuration is exactly as described in
the README file from nVidia. Then look
in the log-files from X. got to start is:
If there isn't anything try to let TuXRacer
write an log file... if you dont find there anything search the forums again or post
your log files here, so that other ppl can
have a look @ it.