I used to install nvidia driver in Ubuntu with Envy because it’s make things as easy as two or three clicks.But few days ago when I was about to install nvidia driver in the fresh installed Ubuntu 10.04 beta2,I couldn’t get envy from the repository,then I downloaded and install the .run package from the nvidia official page,but I got an error said “failed to load NVIDIA kernel module nvidia.ko”.
Finally,I properly installed the nvidia driver with following steps.

First,open terminal from Applications->Accessories->Terminal and remove all nvidia stuff by this command:

sudo apt-get purge nvidia*

Blacklist the nouveau by adding following into /etc/modprobe.d/blacklist.conf (edit this file and add following into the end of file)

vga16fb
nouveau
rivafb
nvidiafb
rivatv

Install the latest official stable driver from the repository:

sudo apt-get install nvidia-glx-185

you can type sudo apt-get install nvidia-glx and press tab key twice to get available packages and choose one.

Now,load nvidia module (restart and try again if it doesn’t work):

sudo modprobe nvidia

and you can check it with the command:

sudo lsmod | grep -i nvidia

Finally,create the configuration file with:

sudo nvidia-xconfig

Hope this help!