Address book data in application support folder

I need to use two sets of addresses/phones in my address book to sync with two different mobile phones.

When using tiger I used to copy the contents of the (user folder)/library/application support/AddressBook folder and kept it as a backup of each set.

I now upgraded to leopard and deleted the contents of the folder and replaced it with the other set, however the address book appears completely blank. I then replaced the contents of the folder with the original set of files, but the address book appears black again.

I tried to delete the preferences of the address book application, but had no success with that either.

Any ideas on how to recover my "lost" data?