Thanks for your bug report. mIRC only sets the transparency setting for a Window - the actual display of transparency is handled entirely by Windows and/or the graphics driver. It looks like Windows 8 has support for transparency in MDI windows - previous versions of Windows did not. This could be a Windows 8 and/or graphics driver bug or a new feature. mIRC was applying the transparency setting to Windows regardless of whether they were MDI or desktop, as it never made a difference to MDI windows before. I will make a change to the next version of mIRC so that the transparency setting is only applied to desktop windows.
