I haven't experienced this myself but would start looking at duplicate resources (with different resource IDs) in your environment. One thing you also could check is the resource explorer history on the device to make sure that that resource have had the MAC address. In other words to rule out different resources. If you right click on a device and chose start you'll find "Resource explorer".
By right clicking in the device collection view you could also choose to add the resource id column.
If your computer BIOS or an application "hides" the wired network card when you connect to a wireless network then SCCM agent would report that the computer no longer has that MAC address, but I would say that this scenario is more common with wireless network cards.
Tim Nilimaa | Blog: http://infoworks.tv | Twitter: @timnilimaa
No luck with the duplicate resources, all devices have unique ID's....
Resource explorer does contain both MAC addresses, device properties only shows the wireless MAC.
With only the wireless MAC in properties I cannot clear the previous PXE advertisement. After deleting and re-adding the laptop with the wired MAC it is still holding a record of the last PXE Deployment (once deleted the system will PXE boot fine).
I have an additional thread going at the link below.
Any help is appreciated