On a new PC, the system was freezing excessively, so I attempted to install a different graphics driver after having many, many problems with Nvidia's drivers. Afterwards, the system wouldn't boot- not even from a live USB. I got it booted using "nomodeset," but now need to figure out how to reinstall nvidia-current on the hard drive installation from the live USB- or how to boot into a terminal on the HD when I can't get into GRUB.