Subtitle on overlay

Hi!

I have a problem with subtitles... In the begining it was all right, but after a while it started to display the subtitle on the overlay surface (if I understand that correctly, that is ON the picture), instead of puting it below the movie on the black space, where it was until now. I do not have the "draw subtitle on Overlay" option markd in, so I'm somewhat lost, concerning th cause of this. Could anyone tell me what to do?