I have a NAS which has Time Machine support. The instructions were to enter the computer name in one box and the ethernet ID in another so it could create and name the sparsebundle image correctly. Following instructions online, I went to system prefs/network/adv/ethernet and used that MAC address. I plug in the Mac via ethernet for the first backup of 100gb and go to bed. Today, I notice TM backing up 9gb. Odd, but whatever, I'll let it do it's thing. An hour later, it is backing up another 10gb. More odd, since all I did was browse the web today. I go to the NAS and look in my backup folder and i see two sparsebundle files, one with the MAC I created and a different MAC address. After looking in System profiler, the foreign one is the real ethernet ID! WTF. Why is system prefs giving me one MAC and system profiler another? Is TM creating two separate backups or is this normal? I'm confused by this.