hey,
I've noticed that on *:appactive: doesn't trigger when you click mIRC's icon on the tray anymore.
It used to trigger in older mIRC versions (don't remember when the tray option began), and no there's no way to catching clicks on the Icon anymore.

The appactive event wasn't designed to detect clicks on mIRC's tray icon, so it looks like this was a side-effect. I'll see if I can add a specific event to handle tray clicks.