[Users] Big issue with oVirt

Dear, We have updated our oVirt installation to 3.3.1 and now we have the following problem: When we boot a VM: He doesn't automatically chooses a hypervisor, he always takes the same But a larger issue is this one: 2013-11-27 12:37:14,528 WARN [org.ovirt.engine.core.vdsbroker.VdsManager] (DefaultQuartzScheduler_Worker-1) Failed to refresh VDS , vds = 2a8b1829-2235-44db-be12-ac71dc6777f8 : Vostok, error = java.lang.NullPointerException, continuing.: java.lang.NullPointerException Vostok is the server where we try to boot the VM, sometimes the VM comes up, but most of the time they don't... And if I would say to boot the VM on a specific other Hypervisor, he will ga ve the same error, only with the other host(hypervisor) in the error log. Any Idea's? Kind regards, Koen