Well, then - most probably - it could be a codec is missing?
The information ".rar-movies" only means that the movie-file is "rarred"/compressed/zipped/archived and it doesn't (on its own) conclusively tell what possible codec is needed. What kind of movie-file is inside the archive?
Did you - at installation - allow BS.Player to install codecs/filters locally (i.e. for BS.Player's own 'internal' use only, so not interfering with others)?
If not, you can still do this by going to BS.Player's installation folder and running "bspcodecdl.exe" from there.
(
http://forum.bsplayer.com/bug-reports-codecs/2939-list-codecs-optional-if-bs-player-codec-manager-used.html#post8355)
Further, maybe it's even
a better idea to first find out what codec it concerns for the file(s) under consideration?
In this connection please read item (3) of my Help2Help-post (maybe you have to unrar the file first for the utilities suggested there).