Windows 10 [Version 10.0.19043.928]
It looks like your version of Windows 10 was last updated in 2021. This may not be the cause of the issue but it's difficult to be sure.
i have not tested 7.81, but it does exist on versions up to and including 7.79.
Please download the latest version of mIRC and let us know if it still shows the same issue.
Question: Are your mouse buttons swapped by any chance?
