When trying to move a Hyper-V Virtual Server from one host server to another I recieved the following error: 

An error occurred while attempting to change the state of virtual machine SERVER.

‘SERVER’ failed to start.

Microsoft Synthetic Ethernet Port (Instance ID {E4BAFA29-EB7E-4CD9-98A5-59546CEA6AE5}): Failed to power on with Error ‘The specified network resource or device is no longer available.’

‘SERVER’ failed to start. (Virtual machine 2A23B1CF-0758-4AF5-84B1-221BA2A8A90D)

‘SERVER’ Microsoft Synthetic Ethernet Port (Instance ID {E4BAFA29-EB7E-4CD9-98A5-59546CEA6AE5}): Failed to power on with Error ‘The specified network resource or device is no longer available.’ (0×80070037). (Virtual machine 2A23B1CF-0758-4AF5-84B1-221BA2A8A90D)

It turns out the Trend AntiVirus client was causing the issue. To fix it I excluded the Virtual Server Storage path from the scanner. A few other places have suggested excluding just the .XML and .VHD extensions seems to fix it. Also other AntiVirus clients seem to cause the same issue.