Solved missing shading and/or boxes

Hi all,
this started happening in my Windows 8.1, I realized that parts of dialog boxes,
drag bars, other details looked wrong. Here is the the same page
in Firefox preferences, same release, one from my old Windows 7 PC and the one with
the problem from Windows 8.1
is there a setting I've overlooked? I tried regscv32 shell32.dll
but it didn't help.

 

Apologize chaps, it must be a side effect of a few power blips we've had lately.
It was a problem with the monitor, the brightness and contrast digital controls were way out.
I reset it, looks good again now.