No problem, sorry, that was actually my miss. Unfortunately, your layout seems to be put together in a very unusual way...so I'm not sure how to address the problem. Sidebars are typically all in one section -- often floated to the side, but your lower section (the mortgage calculator) is separate from the top part.
I don't have IE7 but I looked at it in Adobe browser lab and it looks like the lower section is the part that is dropping. You might try floating it to the right and see if that fixes the problem - though you'll need to adjust margins for that to work okay.
Beyond that, what I'd really suggest is that you redo the layout...as is, I think you are going to have continuing problems with it, perhaps not just in IE. If you're not experienced with layouts and CSS, you could dissect some other themes using Firebug to see how they are put together.