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

For this feature, you need to be using the web client feature. From the traditional Vsphere interface, you might face this error message.

I am using the web client.

Also, just try to make sure that the hosts are not connected to any other VCs

The hosts are only connected to one VCenter.