I have several different mIRC's floating about my puter without any probs, i just rename everything when i copy them to a different folder (like mIRCtesting). (side note: and of course never install one while you have another one running) Have you compared all the connect options between the two? Assuming you have connected with the "main" mIRC, disconnected and immediately tried the same server with the "secondary" mIRC, odds of several servers on diff ports all being suddenly full and refusing are slim. Are the servers all on the same network?