Hi Derry:
First, you're missing that neither product is supported on ESXi 5.1. At this time, nothing over 5.0 has been tested.
For the MSE to not respond with the settings given during the initial setup script in the NCS communication settings question, something's very wrong with the responses getting plumbed into the system correctly.
Moving both devices to an ESXi 5.0 platform will be the place to start, although will probably require that your licenses be rehosted. That's a simple enough process, just open a service request against Prime Infrastructure with Licensing as your problem, then provide the PAK or current license files and the new serial number.