I'm really puzzled ... that you should get audio files and not video.
IE 7 is probably a red herring
Of course if you download from a host one day does not mean you can another. Their slots may be full or they may be offline. I still think what I suggested before should help ... have you checked the files with bitzi?
Also are you sharing and do you have chat enabled. Chat doesn't work atall at the moment but it can help others browse you if it is enabled. If they browse and see nothing they can prevent you from downloading assuming, often wrongly, that you are a freeloader.
Be patient ..try for files with a low number of hosts.. and let us know how you get on .. I'll be away for a bit but someone is always here