I have an iMac 24", running OSX 10.5.8. I noticed sometimes when I wake my Mac from screensaver, the gamma is off. The screen becomes very white-washed looking. I can get it back to normal gamma by firing up System Preferences -> Display without changing any settings.
I do this every time and it's become very annoying. Can someone tell me what's going on and how I can fix it permanently? I don't have this problem on my MBP.