I recently assisted a customer in an engagement where a Lync Server 2010 Edge Server was being put into production. The server was pre-configured from an OS-perspective by another IT group and handed over to us for application configuration. Setting up Lync was straight forward however we noticed through the troubleshooting process that outbound communication on the External network interface was failing. Further investigation showed the server couldn't even ping it's own IP!
The error was: PING: Transmit failed. General failure.
After looking at the interface properties and TCP/IP v4 properties, we noticed NLB was enabled on the NIC. Unchecking this feature resolve the issue. We fought with this one for quite some time!
Hopefully this helps some of you out there.
Go Windows 8!!!