Hyper-V Machine Creation Error (0×80070037)

On an existing Hyper-V server that was previously working fine, i stumbled across the error below while trying to create a new guest machine.

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)

I narrowed this down to be a combination of a few things.

• I had added a new location for hyper-v vhd/xml files and hadn't excluded that new location from realtime AV scanning
• Secondly, the version of MS Forefront AV client i was running on the server required an update to version 1.5.1958.0
• Thirdly, i excluded .vhd files from realtime scanning.

And don't forget to bounce the server, or at the very least the services for hyper-v afterwards!

Official Microsoft info here... http://support.microsoft.com/default.aspx?scid=kb;EN-US;961804