Time Machine nuking backups, starting from scratch!

Question

ok, i just received this warning:
and now i't doing a backup that is slated to take more than "several hours."
is this common? how often can i expect this?

Answer 1

Hello,
Should you click “Start New Backup”? Not yet! If you see the dialog above, your existing Time Machine backup is corrupt, and you might not be able to recover data from it. But you can save a copy of the corrupt bundle and, perhaps, extract some data from it if needed.
Ask yourself if Time Machine has saved data you might need before deciding what to do next:
If you are sure you won’t need anything backed up before today, click “Start New Backup” and let Time Machine do its thing.
Otherwise, click “Back Up Later” and save a copy before letting Time Machine start a new backup. Just look for a file called “computername.sparsebundle” (for network backups) or “Backups.backupdb” (for local ones) and create a copy with a different name. You can open sparsebundle files with DiskImageMounter and browse them like any other disk. More information is available here.
There you go. If you click “Start New Backup” when you see this dialog box, Time Machine will erase all of your old backup data and start a new bundle. It won’t be corrupt, but it will be empty.
Note that you can manually initiate a Time Machine backup integrity check by option-clicking the “Time Machine” icon in the menu bar and selecting “Verify Backups.”
http://blog.fosketts.net/2010/08/11/time-machine-completed-verification-backups- improve-reliability-time-machine-create-backup/
According to This Time Machine resource   “This appears only on Snow Leopard, and started with the Time Capsule Backup Update 1.0 in mid-May of 2010.  It also seems to have been included in the 10.6.3 v1.1 update and 10.6.4.”
So, what can you do about it?  Grin and bear it, it seems, until Apple fixes it.
One thing you can do to make the backup take less time is to connect your machine to your Time Capsule or other backup drive via Ethernet for the duration of the initial backup.
http://www.theinternetpatrol.com/the-dreaded-time-machine-has-completed-a-verifi cation-of-your-backups-to-improve-reliability-time-machine-must-create-a-new-bac kup-for-you-message-and-why-you-are-seeing-it/
Time Machine: About "Time Machine completed a verification of your backups. To improve reliability, Time Machine must create a new backup for you."...
http://support.apple.com/kb/HT4076