Where are the messages coming from exactly? A switch? A firewall? Anyway you should see that each message comes with a different MAC address (presumably one from each server NIC card) as the VIP (virtual IP) is seen as been connected to two MACs and hence two switch ports.
Now when you configure teaming you should create a VIP and a virtual MAC which should avoid these coliisons so chech the NIC teaming configuration. Also if both server links are connected to the same switch, you might want to configure an etherchannel between the switch and the server to take advantage of the full bandwidth available in an active-active design. An alternative would be to have one NIC connected to one switch, the other NIc connected to another switch and to use Active-Failover configuration, thus avoiding the problem of collisions.
Each company, be it Dell, Microsoft or Intel have their own way to configure NIC teaming on their servers and none of them appear to have taken networking (switches, firewalls etc) into account with their lovely ARP broadcasts and virtual IPs. I don't think they stopped to think about Layer 2 and 3.
Anyway, it sounds like a configuration issue on the servers (the server guys will never tell you that though), but it sounds like you need to sort out how you want the NIC teaming to work and the best way to implement it.
HTH,
Ian
