As far as I know, the theme’s slider should work fine in IE9. I’ve never heard of any problems like the one you’re describing.
However, often when people think their site does not work in IE9, it’s because they’ve accidentally turned on compatibility mode in their IE9 browser. Is this possible?
If this is not the case, please setup an example for me that I can view in IE9 to see the issue. It doesn’t have to be on your homepage; you could try and reproduce the issue on a subpage or something that isn’t linked to your main menu.