Fixed!
Phew. All fixed! It was actually easier than I thought it was going to be. Turns out it only affected pages where I had images in my posts that were wider than what the stylesheet specified. Firefox is fairly intelligent and just resizes those images so they fit the stylesheet. IE sees that they’re too big so keeps the image there and pushes everything else down to the bottom. I’ve resized the offending images and everything is all happy again.
Ok, time to prepare for the MOAB…