Yes, you understood him correctly when you thought he was talking about a shortcut. It's strange you are getting this error...
Since mIRC is a standalone application (it is not dependent on all kinds of registry settings and runs with only the files in the "installation" folder), try to install a new copy of mIRC to a different location and see if you can run it from there. If that works, see what happens when you replace your old mIRC.exe with the new one.
