I've been using the Nvidia 190.42 driver with 9.10 - two 9800GTs and 3 displays without any sort of problem... I'd say the only real difference is that I'm running Gnome, but that shouldn't interfere with the loading of the module.
Stupid question #1: Did you make sure that all other Nvidia drivers are un-installed?
Stupid (or not so Stupid) Question #2: Have you tried dropping to a shell after login, killing X. Then manually loading the module:
and see what the output is?
That may help to identify some more errors. Also, before that make sure there aren't any random modules loaded that would interfere, so lsmod and check the output. Unload anything that looks suspicious.
Also, check /etc/modprobe.d/blacklist-framebuffer and blacklist - something may be causing a problem.