Have you tried editing grub before booting? I believe I had a somewhat similar issue a while back, and adding the parameters for my graphics card solved the issue.
Just press "e" when you're booting and add one of the following parameters to the line where --vga=791 is.
The parameters are:
If you have Nvidia's optimus technology you'll have no choice but to use the Intel card (unless you have an option on your BIOS to use only your Nvidia). I think you can still use your Nvidia for pyrit and other CUDA apps (I got it working on a previous install of BT5), but the installation process is really tricky.
Newer Intel video card: i945.modeset=1 or i945.modeset=0
Older Intel video card: i915.modeset=1 or i915.modeset=0
Generic: xforcevesa or nouveau.modeset=0