Sidebar suddenly disappeared in IE (but not Firefox) browser

I designed my own blog using Artisteer and have been writing posts for several months. Two days ago, I wrote a blog and noticed that the right-hand sidebar had suddenly disappeared in my IE browser (but not in my Firefox browser).

I have tried everything–deleting the post, completely redesigning the template, switching to an old template designed by an expert, changing the width and padding in the blog…and still the sidebar won’t reappear.

What can I do now to fix the problem?