I'm trying to do a back up in Time Machine. It's been going for like an hour and it still says "Preparing Backup." I haven't changed my files around much and it really should only have a couple of kb worth of new data to back up. My last successful backup was yesterday. It's done this a few times since then. I tried to stop the back up and restart it to no avail. I also went into my backups folder and deleted the "in progress" backup then tried to backup again and it's still not working. Ideas?