Well OK, remember that the Media player used is version 9. Maybe your content or video is encoded with some fancy new stuff. Not sure what to advise you really. Maybe I don't understand your problem. What I know is that streaming does work ok for me for PPT files, Photos and Videos.
The only two snags I have are: 1) make my departments save any new content to the original name, as I have only registered files with one name and 2) have my server running all the time - if there is ever a glitch on the network then I have to republish.
Bill