anisotropic setting issue

I'm not quite sure whats going on, i have a 8800gts 640 and in the settings it will not let me choose 4x anisotropic filtering....but it lets me pick everything else. I was playing a game it crashed with some odd looking color triangles etc...so i rebooted figuring if it was the video ram i'd do some benches. Well I ran 3dmark 06 for about an hour card not reaching above 41c and nothing no crashes, no tearing, no anything. So i figured i'd reinstall the drivers but that didn't work. Everything seems to be running fine, except it not letting me put it in 4x anisotropic.....anyone ever run into this or maybe someone could point me in the right direction

Are you trying to force 4xAF in the nvidia control panel, or set it inside the game? If the former, it's buggy, so don't bother. If it's in-game, dunno..

just run with 16X its not that bad

Just bump it up to 16x, even my 6600gt could run 16x anisotropic filtering without any real performance hit. I think the largest I ever got was something along the lines of a 3fps drop for my average framerate.