Make sure you upgrade to the latest mIRC
here (version 6.12).
You may also like to make sure you haven't got a virus, especially if you're getting these types of error messages with other programs too. Try
TrendMicro,
AVG, or if you're willing to pay money (for a better more advanced antivirus admittedly) try
Norton AV or
McAfee.
You may also like to use the
Search function and search for other posts like this. Expand to 'All Forums' and search for the 'Entire phrase' and expand the Date Range to 'All Posts' - I find searching for "Stack dump" is quite productive on this subject.
G'luck.
Regards,