Web results:
I had this and after looking at /var/log/Xorg.0.log I found out that it's a Nvidia problem (there was a line saying Xlib: extension "GLX" missing on display ":0). I realized I have Nvidia drivers from official website which are not really stable and tested (so I've read and also experienced in the past).
We would like to show you a description here but the site won’t allow us.