Hyper-v: The Application Encountered an Error While Attempting to Change the State

  Today I was configuring a server with the Hyper-v role and without paying attention I picked the wrong hyper-v generation. When I attached an ISO file to boot from, so I could configure the virtual machine I received this error - "Synthetic SCSI Controller (Instance ID AC2FB770-77F1-4E0C-9E91-C66766022B89): Failed to Power...."

This error came about because of picking Generation 2 during the virtual machine setup.

The way around it is to delete the VHD file and re-create the virtual machine, but make sure you pick Generation 1.