I have an external 3 TB hard drive with a partition set aside for time machine backups. I decided, for whatever reason, to reformat the time machine partition and start it over.
Now, I see this. Bear in mind, this is over FW800.
Try this. Stop the TM backup and reformat the drive. Then open Spotlight prefs and drag Macintosh HD into the privacy settings to disable Spotlight on the main drive. Then drag it back out to reenable Spotlight. Wait for the Spotlight reindex to complete then try the TM backup again.