Have a 5850(1gb), I think I have had this problem ever since new, but it finally discoverd it was the card the entire time.
When I first bought my 5850, I had it connected to a single 24" (245BW) + a 32" TV. I always had gamma problems on the TV. I thought it was because of differences in the greyscale on video vs. pc. I tried some work arounds but never got it setup great.
Now I have 3x 24" monitors on my desk, 2 via DVI, and one displayport.
Which ever monitor is connected to the lower DVI port is very washed out in the high end. 86% to 100% all just look white. Darks look ok. Its not the monitor, if i swap the cables my other monitor has the problem now.
I cant find any settings in windows that have been adjusted to revert. Also when I use eyefinity mode, all are seen as a single monitor and any custom per display settings in windows should not work? In eyefinity mode the single monitor is still very washed out on the high end.
In CCC, if I adjust "desktop color" (only setting with gamma) all the way down as low as it goes to .5, the high end (whites) looks fairly right on the bad DVI port, but at the same time destroys the darks (0-15% all look black). With eyefinity the only adjustments I can really make are "Display Color (digital flat-pannel)" or using the built in adjustments in the monitor. Either one gets it nowhere near close, if i bring the high end down it always destroys the low end.
I am the only one to ever have this happen? Could it just be a bad cap/resistor or something that i can fix?