Well, that happened to me also.
The problem is that the method ClusterMonitorImpl.getMSAddress is looking for the MS http port of the SCS message server. In our case, we had a problem with the port (it was used by our backup tool) and the SCS MS Service was only running with the internal port 39xx and it could not bind the http port 81xx.
The exception (java.lang.NumberFormatException: null) suggests that your Message Server could not bind the HTTP port.
Well, it is too late, but if it happens again, check your dev_ms file in your SCS instance. Chances are that you have the same problem with the binding of the HTTP port.
Regards
Abraham