while installing nVidia on kernel 2.6.9-1.639 FC3 warning about rivafb module

[Alor]

While installing nVidia driver 6111 on FC3 test 3
with kernel 2.6.9-1.639 I get message:
WARNING: Your kernel was configured to include rivafb support as a
loadable kernel module.
After installing and setup in xorg.conf nvidia
the system is not booting.

After replacing nvidia by nv in xorg.conf is OK. but not nvidia
driver.

What is rivafb and how can I it disabled?

Best regards
Alor