Reboot and select recovery mode from GRUB. If asked, select to drop to a root shell and execute:
Just answer yes and ok to all the questions. Then type exit and then select resume normal boot. (or reboot your computer as normal).
If that still didn't work, get back into recovery mode and open your xorg.conf:
Then move to where it says "Device" and add - Driver "vesa"
right below the "Device" section. Make sure it's Driver without quotes and "vesa" with quotes. Then hit ctrl-x then Enter to save your settings & reboot as normal.