You playing around with grime variation in your material? Cause it exactly like what tea said where your diffuse is moving. Post up the material network if you can.
Try this: http://www.polycount.com/forum/showpost.php?p=1358076&postcount=19 You might also want to add NOTEXTURESTREAMING to the shortcut just to be safe. I'm not too sure if that's a lightmap issue though. Looks like the scratches on your diffuse change their position along with the angle. Weird.