World of warcraft video settings

I usually flick between full screen and window mode on wow. When i take it out of fullscreen the image darkens, becoming saturated and blotchy, but when i flicked back to fullscreen what i assume were the correct settings would re-assert themselves and the image would lighten and sharpen up. But now the bad settings have somehow been preserved and are re-applied even in full screen gaming. I now cant make out a lot of detail and routinely fall off things because objects are almost indistinguishable from shadowed areas Has anyone else had this problem? or does anyone have any ideas as nothing i try works.

thanks