I've had problems with Mirc using incorrect ip details and such before. They were usually resolved by going into the tab where you have the host info, ip etc and switching either to or from the server option. I don't actually know what causes the problem though.
I actually no longer use Mirc, I use X-Chat 2. It took a bit of getting used to at first as Mirc had been the one and only client i'd ever used since I started on IRC a couple of years ago. I find it better for scripts and things and have never had connection problems with it except for when the IRC server itself was experiencing a problem.
Edited by Kurasaki_Ichigo, 18 September 2006 - 08:50 PM.