I think I'm seeing something similar with some buttons/icons on Firefox's (FF14) Add-on Bar that occasionally appear grayed out.
The status/settings of the buttons remains the same as what they were when they appeared normally, but the background of the icons have a grayed out appearance.
Toggling Firefox's Add-on Bar off and then back on again (using Ctrl+/) brings back a normal appearance.
I didn't start seeing this behaviour until recently after I upgraded Xorg from 1.10.6 -> 22.214.171.1242 and the 173xx driver from 173.14.31 -> 173.14.35
This is on a Debian sid install with a 3.4 kernel, KDE 4.8.3 and a FX5200 videocard (there's probably more thorough system details in the attached bugreport)