The OCC forums will be going down soon for a major software upgrade. I was told by the admins that they will be down for two hours at most, and that it could take less time than that. When the forums come back the OCC theme will be temporarily disabled and a standard theme will be used until the forum software is configured. The full site won't experience any downtime.
Update: The forums are now up but not yet rethemed. For more information or to report an issue, visit the forum thread New Forums.