Psp problems

My psp will not play some of the downloaded youtube videos via psp youtube downloader/ psp video 9 nor will it play rpped music, it has before but won't do it now, why? What can I do to fix it?

I found that sometimes videos I convert with video 9 won't play. Usually if I try some different conversion options I can manage to get the video to play. By leaving all the options at default my videos play most of the time; when I try to improve the video quality is when I usually have problems.

I've been thinking about trying one of the commercial packages for this since Video 9 is a little hit-or-miss.