The line in the modules.conf file should be alias char-major-195 nvidia
Loading with warnings MAY be ok if it's the taint warnings. Again, use lsmod after manually inserting the module and verify if it's loaded. If so then restart X after changing the XF86Config file. Logging out and then back in to X should restart the X server.
What warnings did you get when you did the modprobe?
I get a feeling that we're going down a traveled path....