The current fragment manager UI allows a pulled fragment to be added to a pushed
fragment. When this happens exceptions are thrown at different points in the
aggregated layout manager and the only fix is to go into the database and remove
the offending pushed fragment manually.

Procedure to reproduce:
Get 2.3.3 release from CVS
> Run initportal
> Login as admin
> Edit Preferences
> Go to the fragment manager
> Create a new pushed fragment and add content to it
> Publish fragment to everyone
> Save Preferences
> Go back to fragment manager
> Create a new pulled fragment and add content to it
> Publish fragment to everyone
> Save Preferences
> Go back to fragment manager
> Back to edit preferences screen
> Save Preferences
> Exit Preferences
> Logout
> Login as admin
> Edit Preferences
> Go to the fragment manager
> select the pushed fragment you created
> add content
> select the pulled fragment under the fragments group
> Add it to the pushed fragment

The exception may not manifest itself immediatly. It seems to occure at
different points each time the issue is re-created.