I get the same error, and I can also stay and chat as long as I don't click the "Send Error Report" or "Don't Send" buttons.
The details of the error seem to indicate a Winsock problem:
AppName: mirc.exe
AppVer: 6.1.2.0
ModName: ws2_32.dll
ModVer: 5.1.2600.1240
Offset: 00003b2c
One of Microsoft's wonderful patches (IE Update KB832894) recently broke a lot of programs that use Microsoft Visual C++ and Winsock . I think that something like this update must be included in a default installation of Windows XP Pro, because I didn't have that patch installed, but I was experiencing exactly the same problems as the Win2K users that did have the patch installed.
The developer of one of the other applications that I use that was affected by this problem recompiled using a 3rd party Winsock libarary, and everything worked correctly again.
I don't know if this is causing the problem with mIRC or not, but it might be worth looking into.
For now I'm using Chatzilla, but I really wish that I could get mIRC to run on my XP machine.
