Why is the Main Column of Wiki Not Displaying in IE9?

All of a sudden, my wiki is not displaying properly in IE9. The middle column, where all the main content goes, won't actually load. There's just a thin, rectangular, white box there. It works on all other browsers. It's strange because I don't think I changed anything on the server and I don't think IE9 had an update recently. Any idea what is going on? And no, I can't simply use the other browsers, so please don't suggest that.