[gizmo]

Without looking at it, I think it has something to do with your css >
#center-main {
padding: 0px 80px 0px 80px;
margin:0px 0px 0px 200px;
}

You have margin left 200px, it could be this that is breaking it, the only way to eliminate and find out what is causing issues, as I do is remove certain css, save > View and see what happens each time in IE8 this is hard to deal with, without anyone physically trying various edits with your css code.

That's the way I would deal with it.
I gather this is a 4.3 install?

Sorry Cannot be of more help.