Server is assigned IP by GUID rather than MAC address in DHCP

I recently installed 8 new Dell PowerEdge c6220 II servers with dual 10G ports with CentOS 6. Each server has a DHCP reservation configured from a Microsoft 2003 DHCP server.

I am using a Bootutil program by Intel that enables PXE booting with these NIC's as required based on a solution provided by Dell support 2 years ago. For some strange reason, 5 of the servers are getting aDIFFERENT IP address during the PXE boot process, but when the OS boots, the reserved IP address is correctly obtained.

I have searched the DHCP server for the IP that it obtained during PXE boot and noticed that in the "Assigned IPs" pane, under the unique identifier column there is a GUID number rather than a MAC address like it should be.

I deleted the entry and tried re-adding the reservation, but nothing works. For example: a host with a reservation for 10.0.0.10, obtains another IP address during PXE boot. But after the OS boots, it obtains 10.0.0.10

I would appreciate it if someone could help me figure out the problem.