And is the Nvidia driver you installed the latest (260 series)? And did you also install "dkms-nvidia-current" to get the Nvidia Settings GUI?
Going into Synaptic and searching on Nvidia, reveals:
One thing -- I did not select these Nvidia modules.
During initial boot of the LiveCD, the loading would only go so far and then the screen would blank. I guessed the LiveCD had tried to install the NVidia driver. So I booted the LiveCD in VESA mode and then installed to the hard disk. After the new install, I did an update with synaptic and I assume these modules were installed at that time.
What would be a good method to troubleshoot this down?