Cannot reconnect to my Time Machine backup

I have three Macs in house, two portables and a Mini running as a "sort of" server (holding file-sharing volumes, but not running Mac OS X Server). One of the external drives (a shared volume) on the Mini is dedicated to Time Machine, and the other two Macs back up to that over the network. The server machine stores its backups in the local fashion (Backup.backupdb), and the other two have their own sparseimage files. It's been working well for years.

Recently, something I did while generating my quarterly backups to another (safe-deposit) drive caused my personal Mac to "forget" its association with the sparseimage file.

I executed the procedure found at http://pondini.org/TM/B6.html TWICE. I turned off TM and ran the two commands

sudo tmutil inheritbackup /Volumes/Time\ Machine\ Backups/CDT.sparsebundle

(then after mounting the sparsebundle)

sudo tmutil associatedisk -a / /Volumes/Time\ Machine\ Backups\ 1/Backups.backupdb/CDT/2014-01-01-145410/CDT

(then unmounting the sparsebundle)

The commands were successful, the first reporting "Claiming disk image for machine," and the second returning silently.

Then I stopped the backup process, and did a "backup now." I got the message about "The identity of the backup disk has changed," and it created a new sparseimage anyway.

I stopped the backup, deleted the new sparseimage, and tried the sequence again, this time stopping TM, stopping backupd, deleting the plist, and performing the commands. This time, no "identity" message, it just created a new backup.

Both machines in question are running 10.8.5.

It appears that the "reclaim your backup" instructions on this page may no longer work in Mountain Lion. :-(