Navbar Line problem in Internet Explorer

I've racked my brain for ages trying to figure this out so I thought Id bring the problem here because I'm at a dead end.

I can't figure out why in IE when you hover your mouse over the nav bar a line appears underneath the buttons. I've coloured the line red to help illustrate the problem.

Does anyone know what's causing the problem? Because I can't figure it out.

You can find the page at

http://www.acwebdevelopment.com/8020/

OK nevermind, just gonna roll with a different nav bar.