Some areas of the window are not redrawn and consequently useless areas remain on screen without deleting.
Develop games in your browser. Powerful, performant & highly capable.
that might be your graphics card driver bug.
my buddy has the same problem, while i don't.
update your drivers and then try again
I had something like that while using C2 on my laptop too.
You should try to "reset dialogs" in the preferences, that fixed the problem on my end.
I have updated drivers.
For my tests, this does not happen with a Aero theme selected.
This happens if you have a custom theme on saving resources, non-transparent windows etc ...