Your right I suspect as I have had this problem myself; it is boot-able, but it will break the Xserver in such away that it can't even change to text only terminal to fix it. So I have to go into single user mode uninstall and reinstall the graphics driver then reboot, and it magically works again. I think it is the installer breaking if there is a old copy installed already rather than a bug in the actual driver itself. This happens every 3-4 months on my Ubuntu gaming laptop.