I'm not sure what I may have goofed up during the install of the nvidia driver, but now whenever I boot up my PC (into FC6), it gives me the textual login instead of the graphical. So I have to log in as root, type 'init 3', hit ALT+F1, and then type 'init 5', and then I get the graphical login.
Did you update your system? If not, yum update gdm and rhgb. On the stock versions of rhgb and gdm when using FC6 I have encountered this issue with FC6 and NVIDIA.