Ideally I'd like to work out what is going on with RocketThemes templates. I think it's a simple Mootools version conflict - even the newer ones I've used are still using mootools 1.0. We're on 1.1, and I think 1.2 is about to be released.
One of the problems is I'm not a RocketTheme member, so I can't get into the forums to start a dialog with the author(s). If you have some contact details I could use, I'd be happy to talk to the RocketTheme devs, and see what we can work out.
Not quite sure why this conflict shows up in IE and not FireFox, though. And because I haven't yet found a decent JS debugger for IE, I can't get much further with your page.
-- hugh