Getting the similar error here, this is a fresh install of Rev. 2 I used the IONetworking.kext provided above and that got rid of the MAC Address cannot be found error.

3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Backup requested due to disk attach
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Starting standard backup
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Error: Volume at path /Volumes/Backups does not appear to be the correct backup volume for this computer.
3/19/08 12:31:56 PM /System/Library/CoreServices/backupd[179] Backup failed with error: 18