Twenty-Eleven Theme Problem

Some of my pages are not displaying like the other pages. They no longer have the sidebar content to the right. What should be in the sidebar is underneath the other content even though the sidebar template has been set. This is happening to 4 of my pages out of 14. I had my host techs look at it and they don’t see anything different from how I set the other pages. They said to contact the theme developer which is what I am doing.