If you notice your navigation has gone away and you have a tab called “Error:”, you have a problem. You may also notice that authenticated users can’t navigate your site.
This is caused when you have setup the Site Collection output cache with “Page Layouts can use a different page output cache profile”.
Here is an another article explaining this problem in more detail.
http://www.sharepoint-tips.com/2007/09/wrokaround-error-in-navigation-when.html
posted @ Friday, December 04, 2009 6:24 AM