Description of problem:

when I press Alt+F2 to open "Run" window, gnome switches to text mode - to go back I need to press Alt+F1. 

How reproducible:

on two different machines (Dell Latitude D620 and Dell Precision M4300), it started to happen after latest update (yesterday) and it happens only after I spend few hours working

Steps to Reproduce:
1. Work for a few hours
2. Press Alt+F2
  
Actual results:

Gnome switches to text mode, Alt+F1 takes me back to Gnome, I can see white square which after a few minutes redraws in content and I can use "Run"

Expected results:

to be able to use "Run" without being switched to text mode

Additional info:

I run Eclipse, Firefox, Evolution, Pidgin and VirtualBox.