[Zope] Can't access management page.

I have a small internal site I have been running for about a year. Starting today, when I browse to the base /manage page, I get the normal tree display in the left hand pane. The right hand pane, however, displays the base page in its presentation form rather than showing the list of objects in the base folder. Any ideas on what may have been changed to cause this behavior ?? Any ideas on how to get it back to normal?? Thanks for the help. Joel jjanosky@freeasyst.com