I don't really see how your inability to trade karaoke mp3s is an urgent issue, so in the future you should probably refrain from blowing your threads out of proportion.
That said, type /debug @debug and then /join #somechannel -- show the relevant debug log. There should be two instances of "JOIN" in the log, one from you, one from the server. If this is the case, you can indeed join channels.
Secondly, in mIRC type //echo -a $os $version $md5($mircexe,2) $script(0) $dll(0)
Paste the results here.
Thirdly, you should attempt to connect to the server with a completely clean copy of mIRC-- that means WITHOUT the OmenServe script. It could very well be the issue.