After a restart of our vCloud Director we had found out that it had a problem connecting to the vCenter proxy service. Researching the problem with the VMware vCloud team identified a potential lock/db cras of the quartz database as the reason. The following procedure helps you identify and fix the scenario.
Please note that this is not an official VMware KB article, so you might open a SR with VMware first.
None of the cells have a vCenter Proxy service running