OCS 2007 R2 and Windows 2008 Domain Controllers

Burried on page 329 of the OCS 2007 R2 Planning Guide is this important note about Windows 2008 Domain Controllers: 

Windows Server 2008 Support

Office Communications Server 2007 R2 supports Windows Server 2008, both for servers running Office Communications Server and for domain controllers. For a new installation of Office Communications Server 2007 R2 in an Active Directory forest that already includes at least one Windows Server 2008 domain controller in any domain, the installation of Office Communications Server does not require any extra preparation and will install successfully.

If you have an existing Windows Server 2003 forest running Office Communications Server and you upgrade any of the domain controllers to Windows Server 2008, Office Communications Server will not work correctly. Some user interface elements disappear, and you will be unable to add Office Communications Server servers or pools. To resolve this issue, rerun the Active Directory forest preparation step by using either Setup.exe or LcsCmd.exe. For details about using Setup.exe to run forest preparation, see Using Setup to Run Forest Preparation in Preparing Active Directory Domain Services for Office Communications Server 2007 R2 in the Deployment documentation. For details about using LcsCmd.exe to run forest preparation, see Using LcsCmd to Run Forest Preparation in Preparing Active Directory Domain Services for Office Communications Server 2007 R2 in the Deployment documentation.

Keep this in mind when upgrading your domain controllers to Windows 2008.