Safari Extensions do not show up. How do I fix that?

As you can see below, my Safari Extension tab does not show. My Mac is up to date on the lastest Mountain Lion. I have had this issue for a while now.

The guy at the Genius Bar did not know how to fix it either. He did temporarily fix it, but he told me that it would most likely go back.

Does anyone have an idea about what the issue is, and how it can be fixed?!