Comment 74 for bug 546578

Incidentally, I can demonstrate this quite reliably on my Intel box by doing "xgamma -gamma 0.5" from within my X session whilst it is active, then switching to a VT and doing "DISPLAY=:0.0 xgamma -gamma 1.0". On karmic, the gamma goes back to the correct value in my X session on the inactive VT, but it stays at 0.5 on lucid despite the X calls completing successfully (note, this tests the XF86VM gamma fade only).

Sarvatt said on IRC that ATI and nouveau users are experiencing the same behaviour too, it isn't limited to Ubuntu, and disabling fading fixes it. My computer with the binary nvidia driver is not affected by this though