The irc:// link will make the most recently opened mIRC connect to the specified server/network. In other words, open the trivia mIRC first, then open the Invision script mIRC, and it should trigger with Invision. As far as I know you cannot force IE to choose a certain mIRC. By the way, I tested with this 6.12.
There have been numerous threads concerning this issue. Perhaps you'd like to run a
Search - Expand to 'All Forums' and expand the date range to 'All Posts' for best results.
See if
this thread sheds some light.
G'luck!
Regards,