Client Hyper-V in Windows 8 : Synthetic Ethernet Port: Failed to finish reserving resources

I am unable to run any of my virtual machines with a network connection.

I get this error when I try to start them:

Synthetic Ethernet Port: Failed to finish reserving resources with 
Error 'Insufficient system resources exist to complete the requested service.' 
(0x800705AA). (Virtual machine ID 8787....-....-....-....-........)

Does anyone know how to fix it?

This is an error from the Hyper-V Manager, in my case, in Windows 8 pro, but also possible to occur in Windows Server 2012 R2.

It turns out that my VMs somehow had two virtual ethernet adaptors, one of which was mapped to an adapter that had been removed from the "Virtual Switch Manager".

Right clicking on the settings, locating the second adaptor, then going to the right side of the screen and clicking the Remove button below the Network Adaptor's configurat properties list, solved the problem.

The error message could be better. Maybe it could say:

"You have two ethernet ports on this VM. Network adaptor #2, has an invalid configuration. Repair or remove the broken network adapter and try again."