Thanks for your bug report. Please type the following command into mIRC and post your results:
//echo -a $os $version $beta $md5($mircexe,2) $file($mircexe).sig $alias(0) $script(0) $dll(0) $com(0)
Please also install a clean copy of the latest version of mIRC, downloaded from the mIRC website, using the Portable option in the installer, into a new, empty folder (such as a Documents/mIRC folder), with no scripts, addons, etc. and run mIRC from there with default settings. If you run this copy of mIRC, do you still see the same issue?