I get this from time to time, looks mad. Almost like shards of nodraw when I move my mouse around in the 3d window. For me its displacements. You should be able to pinpoint the displacement thats causing this error my deleting each displacement, checking if you still have this then hit ctrl+z (Undoing it) if its not the problem displ. until you have found the problem displ.. Bit if a pita but it saves redoing loads of work again. Once you have got rid of this effect in the 3d window you know then which displacement is causing it so you can redo that one and only bad displacement.