He notes on this page of the “0.2.2 Feedback” thread that both the Radio and Look for shared music bits have been checked, deselected and rechecked.
Based upon the description of issues involving both iTunes 4.9 and iTunes 5.0, I would be inclined to suspect something with mDNS beacon on the server. Just because it appears in the process list does not indicate it is properly broadcasting. Also, are you running both mDNSResponder and Howl? You only need one or the other and may be experiencing a conflict there.