Yes, I have a nvidia card (GT 8800 512).
But I don't think that this is card related. Your firts pic at stock 1024x768, when using the WS mod, the image must be elongate in it's high (with black bars at sides). In your pic it's normal, not elongate. So, will not fit in correct WS. IF the mod was applyed correcty this must be not happen (viewport right from 1,0 to 1,4 deforms the image).