domain-c7 is a Managed Object Reference to the cluster compute resource according to vCenter (kinda like a database index).
what it's saying is that the cluster was prepared and failed previously, so there is some mapping to it.
I have seen this error before, but it's best to file a support request with our vShield/vCloud Network and Security support team.
If this is a BRAND new deployment, you can just power off/delete vShield Manager and replace it with a new version. If you do, make sure to deploy 5.1.2 and apply the 5.1.2a maintenance bundle from the download page.