Q Somehow I created a Smart Group in Contacts, and now cannot sync it using Syncmate with my iPhone 3gs. Should I trash Contacts and reinstall it and my backed up Address Book, or what?
A A Smart Group is just a subset of your main Contacts list, created by means of a rule. It could, for example, be all those people with a business phone number. That should not cause problems with Syncmate, so it is worth checking with its help desk that it is not a known issue.
It is probable that your Address Book has become befuddled. The best way to deal with that is to replace just its data files from a recent backup. Your Address Book data used to reside in the folder at ~/Library/Application Support/AddressBook, within your Home folder.
However address books are now stored in sandboxed ‘containers’. To locate yours, browse the Library folder in your Home folder (~/Library) by holding the Opt key and opening the Finder’s Go menu: you will then see Library listed as one of the locations.
In ~/Library, address books are stored in the path Containers/com.apple.AddressBook/Data/Library/Application Support/AddressBook. Currently this is an alias which points at the traditional path of ~/Library/Application Support/AddressBook after all, but that could change at any time.
If you are certain that you have a full backup, then you might try moving out of that folder the files with names starting AddressBook-v22 to another safe folder, then replacing those files from the last backup made before the problem arose. If that does not fix it, you could also try replacing the Contacts app itself from backup, before considering any lengthy reinstallation.
Updated from the original, which was submitted for publication in MacUser volume 31 issue 3, 2015, but never appeared.