Sidebar drops below comments in Flexibility Theme

Hi,

I tried looking for a fix for my problem but cannot find one that works. It seems to be quite a common problem.

The sidebar in my blog drops below the comments when I go to a single post. But its fine when I view it at my homepage. I have tried everything thst other people were suggesting like adjusting the width, checking the codes, etc but I just can’t seem to fix the problem.

My url is http://fish-tank-filters.org

Please help me!!!!

Thanks

Tim