Time Machine "disk ran out of space unexpectedly"

[Candlelight]

I'm just started using time machine so I'm not that familiar with it. After about a week I started getting an error that my drive is full and it can't back up anymore. But when I check there's almost 170GB free (on a finder level) but 24GB within the time machine preferences.

I thought time machine deleted old backups as it goes?

I'm running 10.8.5 on a MacPro3,1, using a 1TB time machine drive. There's about a dozen or so successful backups so far.

 

[MC6800]

I think Time Machine can get stuck if it had made enough space on the backup drive when it started the session, but files where added or enlarged while it was working. It will keep trying to continue that session but fail. Try deleting the last in-progress backup first.

 

[Candlelight]

OK, cheers, will try that.