ph1a5h, are you using a nvidia card? If so, the solution I gave here
should do the trick.
I don't think killing X is what caused the problem. If you had need to restart X I'm guessing it's whatever happened just before the restart that caused the problem.
PC: LMDE x64 MATE/Cinnamon, Kernel 3.9, Nvidia GT620, i7 3770K, 16GB RAM
Laptop: LMDE x64 MATE, Kernel 3.8.6, i3, 6GB RAM