I'm running VSC 4.2.1 and have recently upgraded to vCenter server 5.1 (which includes single sign on). VSC now gets authentication errors and I suspect it's because of the new vCenter server single sign on. I had to rip out VSC and reinstall it to get it working. In that process I had to use different credentials (running as the administrator instead of using the service account I had set up) to get it to work. That was my hint that I've got an authentication problem with the new single sign on functionality.
I've got several systems that use SnapDrive to snap volumes that are actually VMFS volumes. SnapDrive is failing to authenticate it's discussion with vCenter to sort out which volumes to snap, even as the administrator.
I'm assuming that you folks have survived this transition already. If someone has pointers on getting everything happily authenticated with SSO under vCenter 5.1, I'd love to hear about it.