Ever since that update I have had an issue with video not going fullscreen. Youtube in particular but othe rvideo sites too. It will work properly when I first open the browser but going fullscreen and back a few times causes an issue where there is a 5-10 pixel gap left, right and bottom. So the desktop or whatever is under the window can be seen. I have updated the GPU driver a few times, Windows update hasn't delivered anything. Not sure if this is a Firefox issue. Has anyone else had this problem.