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

your both host are on ESX 5.1 and v center 5.1? Because only with  vmware 5.1 you can migrate vm without shared storage as it has enhanced vMotion feature.to checking this issue you can try vmotion with shutdown the vm for time being.