I'm back to this problem. I moved the load from this server to another server so I could further investigate. I think I found the issue, but not a resolution.
In Device Manager, I still have two rogue entries:
Hyper-V Virtual Ethernet Adapter
Microsoft Hyper-V Network Switch Default Miniport
Both of these have the following error:
This device is not working properly because Windows cannot load the drivers required for this device. (Code 31)
An object ID was not found in the file
In PS the Get-VMNetworkAdapter - ManagementOS and Get-VMSwitch both come back with no results, yet they are listed in Device Manager. I can disable them in DM, but it does not resolve the issue. DM does not let me remove them, and Remove-VMSwitch and Remove-VMNetworkAdapter have no effect.
Reinstall Hyper-V Server. Something is hosed. Well I guess in your case it is Server 2012 DataCenter?