today I got my hands on a mac installed the mpeg2 codecs and made several experiments with mpegs made by me and some mpegs I got on the web. The only mpeg that run flawlessly was the one that I created on the first place (the one that wasn’t supposed to work :P). To avoid further troubles we decided for a completely different solution, we made a mini flash application for windows and mac, that plays an flv.
Anyway, thanks for your response.