Could you try as follows (assuming you're using base-skin):
Start-up BS.Player by its executive.
Load a movie-file and click on play.
Increase sound-level using the slider or by clicking on the (+).
While movie is playing exit BS.Player by clicking on the [x] (at top right of control panel)
Now try playing a movie-file.
Result?
If this doesn't work:
Exit BS.Player
Search for file "BSplayer.xml" and
rename it (e.g. in "xBSplayer.xml").
It usually is in the folder:
C:\Documents and Settings\[YourName]\Application Data\BSplayer (PRO)\
or (alternatively) in BS.Player's installation folder:
C:\Program Files\Webteh\BSPlayer(pro)\
Now start BS.Player and play a movie-file.
Result?
(N.B.: The second method will loose your settings; if you don't want that, I can explain how to manually change the file-contents using Notepad.)