Streaming media problems

We are a content provider sending out Windows Media streaming content-mostly at 100k. I have several machines running Win98SE with the IE 5.5 and Windows Media Player 7.1 that will not play the content and I can’t determine why. The flying logos screen just shows, no audio, although the slider bar is moving, and statistics panel show that the data is indeed incoming. The server works fine because I can get it on other machines. Its not a bandwidth issue-I am on a cable modem/ sometimes on thelan. I need to be able support subscribers who will ask the same questions and I can’t figure it out!