Blue Server theme – main content moved

Hi!
I am using the Blue Server theme (by Blue Angel) and suddenly the center portion of my site (holds posts, main content of page besides sidebar) dropped down below the sidebar and makes the page twice as long as it needs to be. I have temporarily switched themes so that the website is still usable, but until I get this issue resolved, I will revert it back to the broken theme so someone here could help me. The website is rosslindsay.com. I have not made any code changes at all or anything.
Any help would be greatly appreciated!
Thanks
Ross