Unsupported data error

I'm trying to put a small movie on my psp. It's now in MPEG-4 (.mp4) format and is inside the MP_ROOT/100MNV01 folder which is on the memory stick. the video is named M4V00001, and comes with a THM file M4V00001.THM.

When I go to play the video on my psp it just says unsupported data. My psp is firmware version 4.05, and my computer is running vista.

I've tried just about everything, but can't get it to play. I've tried putting it in an 100ANV01 folder and renaming the file MAQ00001 etc. Nothing seems to be working.

Now the video will play if i hook my psp up to my xbox with a USB cable, but this isn't what I'm looking for. I can't understand why my psp won't play it.

Any help on this would be fantastic, this is doing my head in. I've put videos on my psp before. But that was some time ago.

What program are you using? It'll be the program.

Strangely the problem seems to have fixed itself. I'm not sure why, but when I tried it today it seemed to work perfectly. Maybe I missed some small detail or something.

Thank you for replying though, I appreciate it.