Comment 12 for bug 165052

Claus, or you have a bit different issue to primary post or you didn't wrote or tested some thing. Primary bug is:
1. first start, mac is correct
2. after reboot or normal poweroff, mac is wrong ( fe:ff:ff:ff:ff:ff ).
3. after complete poweroff ( PC should be _unplugged_ for at lest 10 seconds ) mac will be recovered.

probably you should remove/comment udev and/or interfaces entry's you made.
To exclude other services start machine in "recovery mode" / single mode and check if mac is still fe:ff...
If mac still fe:ff.. set it some thing other for example 11:22:33.... and reboot again in recovery mode.

try to get some more info.
echo "options r8169 debug=16" > /etc/modprobe.d/r8169