WMI errors when running dfsrdiag backlog command

I am getting an error when trying to do backlog report from both powershell & cmd. i am running the command as a domain admin.
DFS-SRV1 is a Windows Server 2008 R2 Std in site 1
DFS-SRV2 is a Windows Server 2008 R2 Datacenter in site 2 (is virtualised  on esx 4)

I have restart the replication service on both servers also tried rebooting DFS-SRV2. I have check that I can connect to all port required using PortQuery and used Wbemtest.exe to check I can access the required Win32_Perf counters.
i have checked that local admin on both has access to \\root\microsoftdfs WMI namespace on both servers

run from DFS-SRV1
PS C:\Users\username> dfsrdiag backlog /RGName:domain.com\shares\Ops /RFName:Ops /SMem:dfs-srv2 /RMem:dfs-srv1
[ERROR] Access is denied when connecting to WMI services on computer: dfs-srv1.belfor-uk.com

Operation Failed
run from DFS-SRV2
PS C:\Users\username> dfsrdiag backlog /RGName:domain.com\shares\Ops /RFName:Ops /SMem:dfs-srv2 /RMem:dfs-srv1
[ERROR] Access is denied when connecting to WMI services on computer: dfs-srv2.belfor-uk.com

Operation Failed