I often had an issue with bsplayer, where on trying to resize the window position, the entire video window would suddenly disappear. No amount of fiddling with various video options in bsplayer would bring it back.

Solution: Delete all bsplayer options to default:

Access this location in Explorer:
%APPDATA%\BSplayer

And delete the file BSplayer.xml in that folder. Restart bsplayer, and voila! Your settings have reverted to default, and the video window is visible.