my structure tab is disappearing!!

Hi all. I must have a conflict that I’m having difficulty resolving. My structure tab disappears and the content doesn’t show up when it is clicked. I’ve disabled all of my extensions except for User, Structure, JQuery for the CP and Fresh Variables.

In the web inspector, I see only these errors:

<a> misnested or not properly closed.  Cloning <a> in order to preserve the styles applied by it.
Unmatched </a> encountered.  Ignoring tag.

Ideas?

Pages is NOT installed