Unfortunately you do not tell how you downloaded those subs.
Did you use BS.Player's feature to auto-download on-line subtitles?
Or did you download manually yourself? In that case where did you save the subs-file?
You can always manually load a specific subtitle using (with a videofile loaded) keycombination (default definition) [Ctrl]+[L].
Also you do not tell what OS you're using.
E.g. try if (de)selecting "Draw subtitles to Overlay surface" under
(rightclick >) Options > Preferences > Subtitles [Subtitle properties]
makes a difference (or "Use new subtitle parser/renderer" which is also under [Subtitle properties]).
