Just read this in the news:  We are releasing SP2 for Office 2004 for Mac today.  This includes much needed fixes to Entourage, the Exchange client for Mac.

http://www.microsoft.com/presspass/press/2005/sep05/09-20EnhancedEntourage2004PR.mspx

It is available at http://www.microsoft.com/mac now.

If you have Entourage clients, for your Exchange server 2003 you will want to make sure you have the fix at http://support.microsoft.com/kb/888619 installed.

(Edit - SP2 is up there now...)