I experienced a similar problem: I tried to install the nVidia drivers on Ubuntu 8.10 Intrepid. When I rebooted the system, I got a black screen. What I found was that the drivers installed correctly but the xorg.conf configuration file wasn't updated. Apparently the black screen results from incompatible resolution or lack of proper configuration. Once I updated the conf file using recommendations found in the forums it worked fine.
I experienced a similar problem: I tried to install the nVidia drivers on Ubuntu 8.10 Intrepid. When I rebooted the system, I got a black screen. What I found was that the drivers installed correctly but the xorg.conf configuration file wasn't updated. Apparently the black screen results from incompatible resolution or lack of proper configuration. Once I updated the conf file using recommendations found in the forums it worked fine.