Home Forums Peripherals & Multimedia Peripherals Invalid node structure on external drive

I was running Super Duper to clone my Mac's internal drive to an external hard drive when it stopped and gave a red error message.

I ran Disk Utility's Repair Disk and got the message that the external drive had an invalid node structure (it made a noise that is reproducable). This external Firewire drive is my only backup. It is a Seagate in an OWC enclosure.

Any ideas on how to fix this drive? It rarely gets used except on monthly backups. (My Mac's internal drive checks out OK).