I think it's possibly something in your header. When I'm not logged in I see your header graphic. When I do login I don't see the graphic, and I see the Active Topics popup in the left hand corner of the screen.
I think there may be some old stuff in your header-insert as well, as I see some things that look like they are coming from an older version.
First thing I'd do is try clearing out your header and see if that fixes it.
