I'm finding difficult to sort this problem out ... Sorry if I'm not explaining myself very well I'll try my best.
I've got the free Platform theme by Pagelines and I've noticed that the primary sidebar (recent comments and facebook widget) on the right all of the sudden shows at the bottom, strarting from the end of the content of the page or posts. I think the content area kind of shrinks as well but I'm not sure if that's related. I've noticed this after I've logged in from my macbook at home. So I had to restore the options of the template to default, this has happened twice.
How is it possible without me changing anything?!
The only thing I can think of is that I've modified the footer, I deleted the image of the leaf linked to Pagelines but it was fine then, it didn't mess up the sidebar, it just happened randomly.
Take a look: