I have recently been having some Address Book sync problems with Office Communicator 2007 R2. A couple things I wanted to share with anyone who cares to listen:
-When you turn on logging within Communicator, the logs are placed in your profile directory. So, at the root of your profile (i.e. for Windows XP, it would be: c:\documents and settings\%username%), open the Tracing folder. This is where the logs are created.
-When you start Communicator, it tries to download and make a local copy of the Address Book. The location of the address book copy is again located in the profile directory. So, for Windows XP, it would be: c:\documents and settings\%username%\local settings\application data\microsoft\communicator .