Nero vision 4 problems

Ive been using nero vision for a while now but have come across my first problem…i have tried to create a dvd of a film file that has burnt on subtitles and i go through the normal procedures and check out the preview which looks fine, but after burning when i come to play the dicsc you can only see half the subs peeping up at the bottom of the screen. this confuses me as the preview was ok. its probably some thing daft but could some one help this noob or at least point me to software that does not have a problem (if it is the software, more likley to be me or the file type). thanks in advance guys