Time machine error: The backup disk image could not be mounted

Question

Time Machine worked OK for several months. Now I get this error every 10 minutes or so.
I unplugged Time Machine capsule and "Change Disk" in Time Machine options.
Nothing helps, I continue to get this error.
I cannot Enter Time Machine either. "Connecting to Server, Connecting to backup" does not work.
Help please because I will probably have to archive and reinstall Leopard. I need the backups,
Christine

Answer 1

Christ1ne,
Before you reformat the disk, consider these causes of this error.
*_"The Backup Disk Image Could Not Be Mounted" (Console - “Failed to mount disk image”)_*
First, it is important to distinguish this error message from another, similar Time Machine error that states “The backup volume could not be mounted”. This is important as the causes and cures for these two errors can be very different.
Consider each topic below separately. When one option does not resolve your issue, then move on the next one.
*Unmount the Backup Disk Image* (TC)
If, for some reason, you have manually mounted the Time Machine backup disk image (sparsebundle), or Time Machine failed to eject it after the previous backup, subsequent backups may fail. (Console - “Failed to mount disk image”… “Backup failed with error: 21”)
Eject the backup disk image (white drive icon) by either clicking the little Eject icon to the right of the disk image in the Finders’ Sidebar, or Ctrl-Click the drive icon on the desktop and select “Eject” from the contextual menu. Now try backing up again or launching Time Machine to view previous backups.
*“Disconnect All Users…”:*
If your Time Machine backup drive (“Backup of Users Computer”) is mounted on your desktop or in the Sidebar of the Finder window. then Time Machine may think the drive is already in use. Alternatively, if the Time Capsule hard disk has been recently accessed by a Windows machine, it may not have fully relinquished control. Do the following:
Open Airport Utility and select the Time Capsule on the left.
Click “Manual Setup”.
Select “Disks” at top of window.
Click “Disconnect All Users…” at bottom of window.
Close the Airport Utility.
Now try Backing up again.
One poster reported: “I got it resolved. Apparently it had to do with one of the files being open on the disk from the drive. I had browsed the disk with one of my windows boxes here and it must have left one of the folders "open". Anyway, I rebooted the TC and we are good to go now.”
*Proper Computer Name* #
Make sure your computer has a proper name. Go to System Preferences --> Sharing. Time Machine needs to differentiate your computer from others on your network (i.e. "Bills MacBook" or "Office iMac"). If the "Computer Name" field is blank, create a name. Realize that if this step is necessary, you will likely have to start the Time Machine backup process over again and do another full initial backup.
According to this article, [http://support.apple.com/kb/TS1760], Time Machine may experience problems if your computer name includes certain characters. Make sure the computer name only includes ASCII characters from the following set.
(0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ)
Once a change in the computer name occurs, you should stop and restart Sharing on the affected computer. Uncheck and then recheck Sharing in the Services list on the left.
# Try removing the apostrophe from the disk images name (sparsebundle).
*A Stalled .inProgress Files:* #
It may be that the previous backup attempt was ungracefully interrupted leaving remains that Time Machine can’t deal with.
Stop any current backup attempt. Choose “Stop Backing Up” from the Time Machine menu.
Open the Time Machine Preferences and turn “OFF” Time Machine.
Open your Time Machine drive.
Open the folder labeled “Backups,backupdb”.
Now open the folder containing backups of the computer in question.
Are there any “.inProgress” files there. Delete them by dragging the file to the Trash. Or Ctrl-Click the file and select "Move to Trash" from the contextual menu. (Give this time as deleting a large file on an external disk can take a while.)
Turn Time Machine back “ON”. Now try backing up again.
NOTE: If the above procedure becomes impossible to perform, try accessing the disk image from another Mac. Some have discovered that attempting a repair from another computer succeeds where the original computer failed.
Let us know if any of the suggestions above helped to resolve your issue.
Cheers!