Do note, you do not connect to mIRC, you connect to IRC
with mIRC. mIRC is one of many IRC clients out there, mIRC is just the most popular one for Windows.
If you're getting that error when you connect, I should imagine it's some sort of ban from a server or network. This has nothing to do with mIRC, it's not an mIRC error message, so check out the information in
this thread.
You could also look at the IRC network's website (if you don't know it, search Google), and look for a server list - try a different server and see if that helps. You may also look for an email address to contact or a forum.
G'luck!
Regards,