i think i get your problem now.
when you are in the edge of a window if you click your middle mouse button then window switches and the previous window goes to background.
if that's the problem, try this:
goto system settings
then look into the second line which says "Action on title bar middle-click"
set it to "none".
your problem will be solved.
the default was "lower" for me. you can set any other options if you like. but in that case remember that it is not only for title bar action , whatever you set it will be set for the window edge too, though it says "Action on title bar".
jahid@HP ProBook 440 G1 Laptop