Only few MOC encountered "Cannot Synchronize Address Book"

Since everything is working fine on your colleagues machines with the same credentials the problem must be local to the machine which is failing.

Try looking in the %appdata%\Local\Microsoft\Communicator\ folder and empty it out.  In that folder you will find GalContacts.db is the local copy of the corporate address book that gets pulled down from the Address Book server to your Communicator client when you start it up.  If Communicator is for some reason unable to write data to this folder at startup (such as file rights issues, disk integrity problems, folder redirection via group policy problems, etc.) then I think the outcome would be similar to what you describe.

If this doesn't work next steps would be providing us with the full distribution group error message you are receiving plus any associated Events from your machine's event logs.  Would also be helpful to know if you are using either of Enterprise Voice or Remote Call Control, and if yes - which one?  

Finally, do some direct verification of your Address list service; Right click the pool name in question in the OCS management console, choose 'Properties' -> 'Web Component Properties'.  Go to the "Group Expansion" tab and take note of the internal and external URLs.  Verify that they are both functioning and accessible from the workstations in question by opening the URLs in a web browser (you should see something like the attached screenshot (ExpansionService.jpg)).

Is there anything else about the failing workstations that is distinct - for instance are they on a different network segment from the functioning ones?

Cheers.


ExpansionService.JPG