That sounds like udev.
grep -rHi eth0 /etc/udev/rules.d/
It will probably show you a file that has a udev rewrite rule for the eth0 and has the mac hardcoded. More than likely in the file /etc/udev/rules.d/60-net.rules
---------- Post added 02-19-13 at 04:37 PM ----------
This could also be ignored if it is infact udev and the nic is working as intended.