Do you use Time Machine to backup your Macs against a local server running Mac OS X server (Mountain Lion)?
It’s been working well for ages but all of a sudden you continuously get “Backup disk cannot be found” errors?
Well if that’s you, there is a simple fix.
When you select the backup disk, you’re prompted to enter the account username and password for the OS X server. Instead of using your account name (e.g. jobbloggs) simply enter your name (e.g. Joe Bloggs) and Mountain Lion will accept it.
Obviously a bit of a bug as either version used to work.