I held a conversation with the Help Operators of Mirc Tonight on this exact same issue.  The information following is what was suggested to me and I am offering it to you. 


It's the server....it is happening to many recently.  It is strongly suggested that you shut down your computer, unplug your modem....re-plug it in so you can receive a NEW IP address.  


The Server does NOT know if you have run your 'virus program' or not...it cannot read your personal computer to know that you have done so.  The Server is causing this to happen, for whatever reason.....and the problem will continue until the IP address that is recognized as an 'error' is not used anymore. 

It is strongly recommended that you do the above - so as to clear out the IP address it is getting from your connection and can read a new one to connect to...or it will continue to happen.

If unplugging and replugging your modem does not work, perhaps you can call your Internet connection and ask them to give you a new IP address with an explanation of the error message you are receiving from the server.  In most cases unplugging and re-plugging fixes the problem right away.

Good Luck!