Sometimes during an attempted Time Machine backup, you'll encounter this message:
Time Machine could not complete the backup. The backup disk image ********.sparsebundle is already in use
This problem may be coupled to the Time Machine drive being mounted in the Finder at all times. When Time Machine backs up to network volumes, it first mounts the remote disk image and then unmounts it when the backup is complete. If the disk image does not get properly ejected then this could make Time Machine think the disk image is already in use. Unfortunately users may not be able to eject the mounted image file, and Mac OS X may give an error stating the drive is "in use".
Fix:
Ensure no AirDisks are in use (if this is the case, eject them from Finder).
Now open the Airport Utility and choose the Time Capsule device on the list to the left.
Then click the "Manual Setup" button and select "Disks" in the resulting window.
Then click the "Disconnect All Users..." button & quit the utility.
Now try to remount the AirDisks...
If this fails, you may need to Restart the Router ...be patient, as it sometimes takes a long time to reboot (will stay on Orange LED for ages).
Now logout and log back in again and re-mount the Airdisks if needed
