That's a good suggestion, but no luck. They recommend cascading windows, but unfortunately Action Browser is not among the windows that appear in the taskbar - whether on or off the screen.
Mmh... I never had a problem like this, sorry.
I use two screens, one for unity and the other one for Playmaker, so I never met this problem, Unfortunately I don't know how to help you. :\
I should try as last chance to installing another version, so maybe the windows position will reset itself.