Hmm the weirdest thing... the bug still exists even when totally uninstalled the game, deleted the whole folder and installed it again without this mod.
The bug triggers every time I do aimed shot now... Even weirder is that apparently it wasn't happening yesterday (I did not modify anything).
Everything (every window too) is half transparent as you can see on the screenshot, just the worldmap is dark.

Do you think I should post it to the Bug section, or does the mod do some changes which can prevail even after totall reinstall? (registry modification?)
EDIT:
After some discussion on IRC, I found out this bug is not related to this MOD so don't fear to use it!