If you are not planning on using the Office Communications Server Monitoring Agent, which is fairly common assumption in lab environments, you likely never planned on installing MSMQ or knew that you had to. Unfortunately, the OCS 2007 R2 setup program does not check to see if MSMQ is installed, and assumes that it always needs to start up the RtcQmsAgent (Monitoring Agent) service on Front End servers. Unfortunately, if you do not install MSMQ, the service will never start up and will trigger service errors.

It doesn’t impede normal operation, assuming you are not using parts of OCS that rely on MSMQ (Archival/etc), until you attempt to install the April 2009 OCS 2007 R2 updates (QFE1).

In particular, KB 967831, will attempt to shut down the services to patch, install the new files and then attempt to start up all the updated services. Due to MSMQ missing, it will encounter a service failure and attempt to revert the patch.

On a bad note, this leaves your OCS Front End install with partial QFE1 (April 2009 – .9) files and RTM (Dec 2008 – .0) files. Even worse, the services will not start up even if you revert the other QFE1 updates for the Front End server.

On a good note, you can install MSMQ to get around the unfortunate "server killer" situation.

With Server 2008, you can run ServerManagerCmd -i MSMQ-Services and ServerManagerCmd -i MSMQ-Server.
With Server 2003 x64, it is a little more complex as an automation task but can be done using the details mentioned here.

The RtcQmsAgent service will no longer fail to start. At that point, you should be able to install all of the QFE1 updates successfully.

Also noteworthy, it is very important to pay attention to which updates are needed for which servers because these updates still don’t seem to be on Microsoft Update and have to be requested individually. The KB article here details which updates are needed by which OCS server roles. Don’t mix and match releases or else you might end up with unstartable OCS services.