Vista Display Settings changing

My Display Setting have started to change themselves on their own. My standard Resolution is 1920x1200 and my colors is 32 bit. At start-up my screen looks like a photo negative. The Resolution changes to a lower resolution or the Colors change to 16 bit, or both. This just started a few days ago. No new system changes/additions or use of Safe Mode recently. Sometimes the screen resolution will look weird and grainy as it is starting up but once start up is complete everything goes back to normal, sometimes it stays messed up. I've run a virus scan, got the most recent Windows Updates. My NVIDIA video card driver is a GeForce 8400M GS with version 8.15.11.8621. I've tried updating that and Windows says it's already up to date (even though Windows online will list the most up-to-date video driver as 8.17....I try to update it to the 8.17 and it just says I'm up to date. Any assistance would be appreciated.