I think I found a new bug (sorry if this is the wrong thread for it, btw!). I'm using mIRC 6.16, and if I /whois myself (chat-solutions.org), I get disconnected:
[10053] Software caused connection abort
It's weird, I know - but that's definitely what causes the disconnet (as I am on a very stable connection, and I tried it 4 times to make sure that was the cause

)