… and you get the little exclamation sign within the Time Machine icon in the menu bar, and Time Machine will not back up your Mac any more, then here’s what worked for me, twice so far:
- Reboot the Mac.
- Before doing anything else, go into the Time Machine drive, locate your Mac’s folder inside the Backups folder, and look for a single file that starts with a date and ends like this: .inProgress. Move it to the trash.
- Tell Time Machine to “Back Up Now”.
That’s it. It should start backing up again. But if it doesn’t, you may want to visit the Apple support forums and see what worked for others. Some are saying you’ll need to toggle the backup disk to None, then back to the usual backup drive.
➡ Updated 8/14/08: Make sure you delete the .inProgress file once you move it to the Trash. If you can’t delete it, do a Get Info and make sure you have Read & Write privileges to it, then delete it. It may take a while to delete it, but let the Finder finish the job, don’t cancel it. If you don’t delete that file from the Trash, Time Machine may continue to give you errors and remain unable to back up your Mac.