Google našel: http://forum.bsplayer.org/viewtopic.php?t=6796&high light=h264
Try going into Preferences -> Video -> Video Rendering
and changing the render mode ie. try 'overlay mode 1' play the file, see what happens, then try 'overlay mode 2' then VMR-9 etc.
usually i find overlay mode 1 or 2 should solve the ActiveMovie Window problem.