My time machine is a 500GB partition on a external drive. For some reason time machine stopped deleting the oldest backup and replacing with new ones. Started saying time machine full. So I deleted the old ones. But OS X can't seem to delete them. Just hangs for days. So then I try restoring them to the original location and it says can't authenticate and/or iMac is in use and can't. So they are all just stuck in my trash.