Posts Are Loading Under The Sidebars

I am using a three column theme with my blog posts in the center of the two sidebars. Up until today everything has worked fine and suddenly my site started loaded funny in IE. When you are on the main page the blog posts all load UNDER the side bars. If you click on an individual post it will load correctly. I have tried playing with the margins, but its not fixing anything. The site looks fine in FF and I haven’t changed anything in a couple months, so I don’t know what happened all of a sudden. Any help would be appreciated!