Re: Error attempting to migrate VM between ESXi 5.1 hosts - Managed Object Reference xxxxx refers to object that no longer exists ??

As a potential workaround, you can try to put into use Quick Migration functionality that is available in Veeam Free version. With Veeam Quick Migration you’ll be able to migrate promptly one or more VM between ESX hosts/cluster, datastores or both. It allows migration of VMs in any state with a minimum disruption to business operations and end user access to services. Cheers.