PostCheck & Lion Bug
I’ve run across a reproducible bug with PostCheck 2.0.2 and Lion. If you add a new address to a contact that already has an address and then use PostCheck to check the new address, Address Book will erase the previously existing address for some reason. I cannot reproduce this in older versions of Mac OS X.
If this happens, you can use Address Book’s undo to revert the change. The temporary work-around is to add the address and quit Address Book so that it saves the changes. Then you can use PostCheck.
I’m looking into the problem now to see if it’s something that I can control.