So if you’re running 10.6 and are using a Time Capsule you may need to wipe out all your old backups and re-backup. Annoying! But make sure you get on it or when it comes down to recovering your data you may not be able to do so. Read this for more info: support.apple.com/kb/HT4076?viewlocale=en_US
Summary
Apple has identified an issue on some Time Capsule systems that could potentially make previous backups unavailable. The Time Capsule Backup Update improves reliability of affected Mac OS X v10.6 systems by creating a new backup.
After installing the Time Capsule Backup Update, you may see this alert prior to your next scheduled Time Machine backup:
Time Machine completed a verification of
your backups. To improve reliability, Time
Machine must create a new backup for you.
Click “Start New Backup” to create a new backup. This will
remove your existing backup history. This could take
several hours.
Click “Back Up Later” to be reminded tomorrow. Time
Machine won’t perform backups during this time.
