[...]
Well... What the hell is that?
It's a common WM glitch. If it happens just zoom in/out a bit and you should be fine.
/Edit:
I noticed the WM is a little out of place if you paly in 1366x768 resolution.
You can fix it by changing the GmapMap value for the resolution 1366x768 to;
GmapMap=0 0 1396 900