When you screw up your X drivers, the following is a good way to force “safe” drivers, assuming you have a bootloader that allows you to edit your kernel boot params like grub.

1. Boot into grub.
2. Edit the boot entry removing extraneous video related entries like splashscreens, and use the following instead: nomodeset vga=791 forcevesa. Generally, depending on your graphics card, vga=791 forcevesa should do.

The tip was based on looking at the SystemRescueCD distro.

Additionally, so I get a more decent virtual console resolution for day to day use, under Debian I do:

1. Edit /etc/default/grub
2. Find, enable if commented, and set:

   1# The resolution used on graphical terminal
   2# note that you can use only modes which your graphic card supports via VBE
   3# you can see them in real GRUB with the command `vbeinfo'
   4#GRUB_GFXMODE=640x480
   5GRUB_GFXMODE=1024x768  

3. Run update-grub2