Cluster Validate Error for Duplicate IP Addresses? Teredo may be the Culprit!

Having issues with networking in a 2008 cluster? Could be Teredo.

Verifying that there are no duplicate IP addresses between any pair of nodes.
Found duplicate IP address fe80::100:7f:fffe%13 on node node1.contoso.com adapter Local Area Connection* X and node node2.contoso.com adapter Local Area Connection* X.

Follow the instructions found here.