Hi, there are so many possibilities of what could be going on. All of which, however, as Ralph pointed out, would be entire guesses without full HTML and CSS :).
Although a link would be more preferable as it would allow easy testing.
I don’t have IE available right now, but I’m assuming the problem is with the quadR div? I couldn’t see any “maincontent”.
I would recommend floating quadR and removing the left margin. That’s always just asking for trouble in IE. I can’t remember how people get that to work (perhaps by adding display: inline?) but I just don’t use that for layout. I don’t see the point, when you can just float both divs.
div rightcolumnFront has a left padding to push it to the right of the left column.
inside this is div QUADcontainer.
inside this is quadL which is float left or quadR.
it appears it is the QUADcontainer that is being pushed over to the right by a similar margin to the rightcolumnFront div. But there is no padding set on this.