Sever creates additional mac address?

I have been running wireshark on my network to see why the users are having “hic ups” when it comes to accessing server resources.

What I found baffeled me…
The sever has 2 nics. One is not even in use.
00 19 b9 b3 cc 7a
00 19 b9 b3 cc 7c < not in use When the client lose access to resouces (which last about a minute) Wireshark shows a third MAC adress comming from my server with a duplicate IP of the server! 00 19 b9 b3 cc 7e <- MAC adress that is causing the problems.. Anyone have ANY idea what is going on? Specs: Sever Model: Dell Poweredge 2950 Nic: Broadcom BCM5708c NetXtreme II GigE (updates drivers still same problem) OS: W2k3