Yeah on 5.1, SSO is rough (much better in 5.5). Will the SSO service not start? If not, vpxd definitely won't run. Is SSO on the same VM as the vCenter or remote? If remote, rinse and repeat the VSS fix for that VM too.
To test your SSO (assuming the service is running) you can login as admin@system-domain using a web client pointed at the VC. If the SSO service is not running (and won't start) you will need to dig through SSO logs and troubleshoot accordingly. While your checking on these things please ensure that timesync is correct on all VMs that participate in the mgmt. solution (VC, DB, and SSO).