*SOLVED*

This is a new one...
I just upgraded my pc and was playing FO3 nicely; smooth with very little stutters. I was using older Nvidia GPU drivers (197.45's); so I updated them to 258.96. Then I changed my settings in the Nvidia control panel as they were overwritten with the new driver set. I changed the FO3 profile in the Nvidia CP and started it up; and I was getting massive slowdowns during action sequences (single digit frames with several second pauses). Thinking I had the wrong settings I checked my profile again and it was gone. So then I tried to add Fallout3.exe again and it won't add it...it just gives me a blank menu where it SHOULD say Fallout3.exe; and the settings don't save.

I'm thinking it enabled AA gamma correction or transparency as it only happens when the screen blurs (while sprinting, getting shot, and in VATS); otherwise I get 50+FPS.

I know this probably isn't a FO3 problem; but does anyone know how ti fix it? It's making the game completely unplayable as I spend more time waiting for the slowdowns to subside then actually moving

Also I have NOT tried reverting back my drivers as after doing some searching other people have gotten them to work; and I really don't want to do the "driver dance" again. I was just hoping for an easy solution I've overlooked.

Thanks for any suggestions
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Update: After searching around some more I found it's a common problem with 257/258.xx drivers. When you select which AA level you want and start the game with Nvidia CP still running; it sometimes erases it. Usually you can add them again; but for some reason I couldn't. You have to restore defaults and they all come back.
Here's some more info on the problem: http://hardforum.com/showthread.php?t=1537930