I have a KMS host on Windows 7. I've used it successfully for Windows 7 and Office 2010 activations. I applied the update that's supposed to make it work with Windows 8, entered the Windows 8 KMS key, and rebooted. However, I still get error 0xC004F074 every time I try to activate Windows 8.
It's not a DNS problem because I also get the error when pointing it directly at the KMS host using VAMT.