I have two domain controllers, both running Windows Server 2008 R2 Standard. One is physical, running as a Core install, the other is virtual, running as a Full install.
The core install was the first new DC added to have R2, it was a fresh install. The previous box had Server 2008 x64 SP2. Once this server was promoted that box was demoted and removed from operations.
Then I demoted the old VM running Server 2008 x64 SP2 and rebuilt it using R2 Full and promoted it to a DC as well.
The VM running R2 Full experiences an error when attempting to add hosts to DNS. The error is identical to this one I found online: http://social.technet.microsoft.com/Forums/en/windowsserver2008r2general/thread/1e68cd26-6874-4be3-9a48-23e55a5aeb87
I have no problems using the core server and adding DNS entries.
Unfortunately a reboot does nothing to help the issue as it did in the case of the above example. I also tried the one other piece of advice in that link and it was already setup that way.