I'll say it again, as Russel keeps saying, you aren't connecting to mIRC servers. mIRC is a client, not a server.
Second of all, there is already a post on that subject to why it happens.
Also, if McAfee can block it so I suggest you disable it to figure out if it is. This will atleast tell you what is causing it. Even though this still leaves the problem of McAfee disconnecting or blocking you from connecting, its better off then not knowing what it was.
I do not use McAfee so I cannot instruct you how to do this, Go to their site or search google for the answers.
