Mouse and backgroud windows

Hello,when I play sc2 I usually close everything behind (sometimes I forget) but even if I do so my bnet friend list opens by itself when sc starts .
Now,when I’m in a match if the mouse is over the backround window cannot click …I cannot move my army ,make buildings,target micro ect.
Even if I forget some window open that shouldn’t happen,it certainly does not happen when I play WoW.
So does anyone has found a solution for this?