Error adding Hyper-v hosts to SCVMM2012 SP1

I'm trying to setup an environment in which I can migrate esxi 3.5 vm's across to Hyper-V (Windows Server 2012). To facilitate this I have installed System Center 2012 Virtual Machine Manager (SCVMM) and have successfully made the connection with the vcenter server i've setup, but the two Hyper-V servers are resisting my efforts.

When I add them as hosts all is well until they are refreshed.

The error is returns is below:

Error (20553)
The Windows Remote Management (WinRM) client on the VMM server cannot process the request. A computer policy does not allow the delegation of the user credentials to the target computer hyper-v1.[removed].

WinRM: URL: [http://hyper-v1.[removed]:5985], Verb: [ENUMERATE], Resource: [http://schemas.microsoft.com/wbem/wsman/1/wmi/root/cimv2/Win32_OperatingSystem], Filter: []

Unknown error (0x803381a3)

Recommended Action
Use gpedit.msc and look at the following policy: Computer Configuration -> Administrative Templates -> System -> Credentials Delegation -> Allow Delegating Fresh Credentials.  Verify that it is enabled and configured with an SPN appropriate for the target computer. For example, for a target computer name myserver.domain.com, the SPN can be one of the following: WSMAN/myserver.domain.com OR WSMAN/*.domain.com OR WSMAN/*

I've checked the group policy on both machines and updated appropriately, however they are a member of a Windows Server 2003 domain which doesn't have the above-mentioned group policy.

I've turned off the firewall for domain and private networks, I'm not sure what else to try.

Any ideas?