I think it's possibly those nasty RPC exploits still going around.
When you get the update from Microsoft to stop your comptuer shutting down, or run a firewall, the virus doesn't actually get removed. So it's still hammering away at other people's connections and this seems to interfier with your irc expirence smile

There's a nice little utility that'll find it and remove it if do you have the virus: http://us.mcafee.com/virusInfo/default.asp?id=stinger

That was what fixed it for me anyway wink