Update: The solution was successful. Public folders have been tested as working. The Entourage instructions have been updated to include the settings needed to see public folders.
A solution to the public folders issue has been provided by Microsoft. In order to apply the solution, a service must be restarted on the Exchange Client Access servers. This maintenance has been scheduled for 6:30 PM on Wednesday, May 7, 2008. The maintenance period should last no longer than a few minutes and should only impact Outlook Web Access users. We apologize for the short notice.