I suppose it's possible that there could be adjustments made to the MAC by the firmware, but if it was the code we would be hearing about it more.
Lycan, you seem to be trying to provide help on this and that is appreciated, but I cannot agree on what you said.
The DGL-4500 suffered from an officially confirmed bug effectively cloning everyone's LAN MAC to exactly what I've got, and yet there is only one person reporting it. Do a search using the LAN MAC address posted above and you'll see.
Anyway, some time ago I started contacting D-link e-mail support. After a few exchange of replies over an awfully long period of time, they are now suggesting me to send the routers back for RMA. D-link is trying to help, and I'll send it back. But now I've pretty much lost all my confidence in D-link's ability to program.