OK, I tried to play your posted subtitle, and... I had no problems with BSplayer! :?
Maybe the problem resides on your PC configuration.
Have you checked
this post as indicated in BSPeter's Help2Help post?
If this can't help you, maybe try to "play" with settings in Preferences window of BSplayer, at section Subtitles.
Check that "Subtitles disabled" is NOT selected
Try to draw subtitles to Overlay surface
Also check the Subtitle position by right-clicking in the Movie vindow then "Subtitles -> Subtitle properties -> Custom position"
I know that BSplayer showed you SSA subtitles, so your configuration should be correct, but try anyway since I have no problems with your file!