Hi Maiden and welcome to the forums!

hmmm.. overlapped windows.. hadn't tried that one. (at work, i cannot try the setup) i do know there is a blizzard weirdness upon button down... seems the mouse position gets reported in an odd way... pushing the cursor to a different location. (i've only noticed it with multiple screens) i wonder if it's happening with overlaps. hmmm...

i'll check it tonight and see what i can find out. for now, to reduce weirdness... uncheck the 'focus follows mouse' and that should help