While attempting to setup an organizations first iPhone on their Exchange 2003 Server using IMAP SSL we were getting errors stating that the username and password were incorrect on the iphone and on the Exchange Server we would get Event ID 680 (Failure Audit):

Logon attempt by: MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
Error Code: 0xC0000064

Finnaly notice that under active directory the user account did not have any UPN login information configured (username@somedomain.local).  I entered their login name and selected the domain information from the drop down.  I was then able to get the iPhone to connect via IMAP.