Hello, dear friends, With F7 on my Dell Latitude D820 Laptop, I have been experiencing this problem for a while, that often some but not all white surfaces appear black and some but not all black surfaces appear white. It used to be, that the problem, if it appeared started with the login dialog, and would end when I restart, but since a little while it also happens sometimes when I want to unlock the screen - and is usually solved when I lock and unlock the screen again. Any idea? Thanks! Take care Oliver -- Oliver Ruebenacker, Post-Doc Researcher Theoretical Biological Physics and Soft Statistical Mechanics Cell Biology at UConn Health Center and Physics at Harvard http://people.deas.harvard.edu/~oliver/