Issues with NLB on Windows 2012

I'm running into an issue when setting up NLB for three virtual servers on vSphere. Each server is running Windows Server 2012 and has a single static IP address. One of the servers has a second NIC with an external-facing IP address. Windows NLB is installed on each server.

I have added the IP address for the cluster in DNS as an A record. It's mapped to a cluster name we made up. Each server has an A record mapping the server name to its static IP address.

When creating a new cluster in NLB Manager, the first server adds smoothly and I can connect to both the cluster IP and the server. After adding the second server to the cluster, we can no longer ping the cluster IP OR the server IP addresses. We are also unable to connect to either server using Remote Desktop, until the VM admin goes in and removes the cluster IP address from the advanced properties of the NIC.

I've tried both unicast and multicast when setting up the cluster, and I've also waited until the first server is completely converged before adding the second. The servers are on a different subnet than my desktop, but I get the same results when pinging from the servers themselves.

One server in the NLB cluster works fine, but two or more seems to result in IP conflict.

Can anyone tell me what I'm doing wrong?