If you’re having trouble using VMware vCenter Converter 5.0 to migrate VM’s with a 5.1 host or vCenter, you’re in luck. vCenter Converter 5.0.1 has been released with support for vCenter/ESXi 5.1. Unfortunately, VMware has not yet decide to support this application fully, as explained in the release notes.
The VMware vCenter Converter Standalone 5.0.1 is a patch release that resolves an issue with running Converter Standalone tasks on vSphere 5.1 targets. For more information, see Converter Standalone 5.0 might close unexpectedly when accessing vSphere 5.1 targets (KB 2033315).
NOTE Converter 5.0.1 is not fully certified with vSphere 5.1 environments. Due to this, some functionality might not work as expected. If you experience any issues, please contact VMware Global Support Services