So, what version are you actually using?
Latest version is 86 build 501 of Sep 6, 2003.
If you are on an earlier version than 500: first install 500
http://www.bsplayer.org/dlfile.php?s...lay086.500.exe
and subsequently place the substituting files of build 501
http://www.bsplayer.org/dlfile.php?fname=bsplay.zip in BSPlayer's installation directory overwriting the exisiting files with the same name).
(another link:
http://forum.bsplayer.org/viewtopic.php?p=6203#6203)
Further: is "Use DivX 4 decoder for ..." on "Video"-tab of preferences checked/selected?
Finally: what type of video (compression codec used) is it? Xvid?