I loved the out of the box RMS feature of Windows Server 2008. Since I am a developer, it was so hard for me to set up a RMS server on a Windows Server 2003 environment.
I set up the Active Directory Right Management Services role in Windows Server 2008 and configured it. You know why? :P To test the MOSS 2007 & RMS integration of course :p
I went to the Central Administration site, clicked on Operations tab, clicked on the "Information Right Management" link and selected the "Use the default RMS server specified in Active Directory" radio button and clicked OK. But all my hope for integrating MOSS with RMS was gone :( I got the "The required Windows Rights Management client is present but the server refused access. IRM will not work until the server grants permission." error.
But I did not quit :P
I gave NTFS read permissions to my default content access account on C:\inetpub\wwwroot\_wmcs\certificationServerCertificate.asmx file and the problem was over. You can give the same permission to authenticated users if this does not solve the problem.