I think you can safely rule out DALnet. I've never been on DALnet apart from when I tried to connect a few times just out of curiosity, to see if I could. I got this error on my usual network, using WinXP Home, and mIRC 6.03. Since I uninstalled XP, I no longer get the error, so for me, I can only assume it was that that was causing the problem.
