I had the same problem before, emailed Khaled.. Here's a quote of what I get in reply smile
Quote:

Hello Alex,

Thanks for the email, apologies for the slow reply.

mIRC should be independent of Microsoft Agent - it tries to dynamically
load the Microsoft Agent object on start up and if that fails it skips
the process and continues running as normal. This is why mIRC also runs
on Windows installations that do not have Microsoft Agent.

It may be that the Windows 7 beta you are using is doing something slightly
different that causes mIRC to crash for some reason - perhaps Windows 7
automatically detects whether an application wants to use a feature that
is no longer in Windows 7 and halts the program on purpose?

Perhaps this needs to be reported as a Windows 7 bug?

I will hopefully take a look at it in the future once Windows 7 reaches
a more final release stage :-)

Thanks again,
Khaled

Also.. in my case it was a system info script that caused it. Scripts like Moo System Info that uses $com on microsoft agent will not be compatible with this. Also some DLL's might cause it.