[Outlook 2010 contacts Business & Home have reverted to all Business]

I keep all my contacts in Outlook 2010 with addresses either Home or Business depending on the contact. Suddenly all addresses have changed to Business regardless of contact. I had this once before and painstakingly went through each on, 646 in total, re doing them. I have no idea why this happened. Anyone any idea please?

 

Not sure why it would happen, but I would back them up on a thumb drive or CD/DVD or something separately then if it happened again, just import them back like they should be.

 

Apologies PeteC for not using correct posting rules.
MrBill. You are quite right of course about backing up. I had done this but it was out of date. I have just spent 2 hours sorting my contacts and have backed the up in two places, I won't make that mistake again.
I would still be grateful if anyone can come up with a possible cause.

 

No, not using Business Contact Manager.