Subtitles with XviD

Hi,

I have an XviD file, and I dled the subtitles for the movie separately. It came in 2 files a .idx and a .sub. I load the movie with BSPLayer and it works fine, then I right click and load the subtitle, which lets me choose the .sub file. I choose it, it seems to accept it, but I dont get any subtitles. Anyone know what the problem coul dbe? Is it that its an XviD? Or does it have something to do with the .idx file. i dont know anything about this, so I would appreicate some help.