I've had my new laptop for a couple of weeks now, and I've been using time machine for months on my old 2010 MacBook Pro with no problem. Last week I got this message about time machine needing to create a new backup, and that my old backup would be deleted. This is now the second time it's happened. My 2010 15" MacBook Pro never had this problem with backups, but this one has done it twice within 7 days. Does anyone know what would cause this problem? I'm really getting tired of having to do new backups every week.