First, you might want to read this link - http://www.entourage.mvps.org/error/page.html#error16008

Two other possible links for assistance
Entourage Help Page <http://www.entourage.mvps.org/>
Entourage Help Blog <http://blog.entourage.mvps.org/>

Another is mactopia - http://www.microsoft.com/mac/help.mspx

Here are some links to specific suggestions:
http://groups.google.com/group/microsoft.public.mac.office.entourage/browse_thread/thread/1a0efbade93b7a58
http://forums.macosxhints.com/showthread.php?t=86804