[HELP] WP sends sidebar to the bottom regardless the theme

A WP blog worked just fine, but now the right sidebar goes to the bottom. I tried with 5 or 6 different themes (that work well in other blogs of mine) but it keeps happening. I'm seeing it with FF (Mac). Other people seemed to have this problem but restricted to IE and/or a specific theme. Should I reinstall WP?

thanks

 

I just fixed it. It was a post with a weird formatting and caused the center area to be too wide.