subtitles
 

when i play films with subs all i see is black screen. what is the problem?

Maybee your font color is black... Check the font settings. =)

It could be a wrong interaction between bsplayer and Dvobsub (you don't tell us what is used for displaying your subs: bsplayer itself or anything else ?)
I've had this trouble:
using bsplayer with overlay mode 2 alone worked fine, using both bsplayer and Dvobsub showed me only a black screen.
Try changing overlay mode or switching to no overlay