I get that and i just wanted to specify some of my comp specs:
Windows 7 x86, GF 8600 GT (253 MB DDR3), 2GB of DDR1 RAM
and BS Player PRO 2.56, build 1043.
I initially had problems with having sound but no picture, but render type changed that (i set EVR :P). So, above mentioned solution is for my OS (Windows 7 x86).
Cheers
Edit: I did find something odd: when old type of sub engine is active (when "use new subtitle parser/rendered" is disabled) the subs stay on screen until new line replaces them!
Activating new sub render type corrected this "fault" :P (corrected to some extent. Apparently subs "stick around" well after their expiry time, until they are replaced with a new line. Quick switching to window mode than again to full screen helps, but only temporarily)