Hi Ryan,
We're looking into this issue. A few other folks have also reported receiving similar Duplicate IP monitoring alerts when they didn't believe there was an actual issue. We think we've identified our DHCP discovery process as the culprit for the alerts. One thing in common with networks we've received reports about the issue on has been the presence of an Apple AirPort on the same network, usually acting as the DHCP server. As I was typing this message, another engineer stopped by my cube and delivered an AirPort to me - I'll now try to replicate the problem here.
I looked through the event logs on one of your sites receiving these Duplicate IP alerts, and noticed that Apple devices were present on the network, although possibly just workstations or servers and not actually an AirPort device. Regardless of what types of devices (such as AirPorts) are causing the issue, I'm hopeful that we can recreate the problem and find a generic fix. Stay tuned.
-mike