I have had the same problem for around a month, dont think its aspect ratio, a third of the widrth of the video is missing.
If you press the display button at the top in the thread details you can change it to its full width, but it also changes how the thread is displayed.

Another problem I am having is since changing to win7 64 bit some of the text is showing distorted, gaps and colour changes.( I have taken into account some of the views on here)