Mirroring system disk fails "could not initiate the locking of partitions"

Hi,

Back-up source: Disk, Partitions & MBR
Back-up format: Mirror disk/partition
Source items: Disk 0 (Track0+MBR, 100MB System reserved, and C:)
Destination: Disc 2 (externally docked)

Error message: “could not initiate the locking of partitions”
Error code: 67 (file not found)

My OS: W7

I tried turning off virus checkers but that doesn’t help. Any other ideas?

Thanks, S