On my internal network, Jplayer plays all of my videos with no issue. However, when I try to play them via normal web access, they just load the preview picture, and never play, or even buffer. It almost seems like it is a firewall issue. That is, inside my firewall, it plays, but outside, it doesn't, although it does see the file, and gives me a preview, different from the .jpg poster view. I never had this problem with Flowplayer, but I don't want to go backwards to Flash.
Also, this is only a problem playing mp4 files, and only mp3 files that have poster .jpgs attached. If I try an mp3 from a direct link, it plays with no problem.
I know this sounds strange, but is there a port that I need to open? Or, is there another non-Flash plug-in that can be recommended?