vSphere storage vmotion fails with error "The method is disabled by '[something]'". If that 'something' is Symantec-ish (perhaps other vendors are the same way), looks like there's a backup which did not complete successfully. A simple solution, albeit inconvenient, is completing a new backup. Once that's done it'll release the hold and storage vmotion can proceed as normal.
Doing further investigation I found other more intrusive solutions like modifying the database, which is more difficult with vCenter Appliance. Another option is to disconnect and reconnect the VM, which is faster but requires power-off of the guest in question.
