Sync contacts stopped working

Question

Recently, I looked for a new contact on my iPhone and it was not there. I then checked the address book on my MacBook Pro and found it. i then added a "test" contact to the iPhone and found that it did not sync to my address book. I sync daily through iTunes and do not knowingly have sync set up to any other source (Palm, Google, MobileMe, etc.). I have 10 groups in my address book, but only sync one or two with my iPhone. The key group is called "Sync Group."
While trouble shooting with Apple tech support, I noticed this problem:
1. After selecting my iPhone in iTunes and choosing the "info" tab and then checking "sync address book contacts" and then choosing "selected groups," the list of groups does not match the list of groups in the address book on my MacBook. I added a "test group" (not a smart group) and deleted a group but neither change is reflected in the list of groups.
Tech support could not explain this.
I suppose the fix will be to delete all of the contact from my iPhone, but before I do, is there a way to filter those contacts that were added manually to the iPhone? If not, those contacts might be lost.

Answer 1

I was hoping you'd say there was a tool I could run that'd fine the corrupt record.
Anyhow, I've tried the following and none of them work (i.e. they don't sync):
i) Adding a new group on my mac but it doesn't appear on my iPhone nor in the list of Address Book groups in iTunes
ii) Adding a new contact to all the pre-existing groups that register in iTunes / iPhone but none of them appear on my iPhone
iii) Removing a contact from a pre-existing group that registers in iTunes / iPhone but it doesn't get deleted from my iPhone
One thing that does work is if I restrict the groups to sync in iTunes then I only get those groups of contacts on my iPhone. The groups haven't been properly synced of course :}
That made me try:
iv) Setup syncing of just one group in iTunes; remove all contacts from it, and add a new test contact to that group but it didn't change the iPhone at all.
v) Try syncing each group individually (I have 7 as it happens) but none sync'd properly.
So I can't use the "what syncs" test to detect the corrupt contacts cause nothing syncs properly as far as I can see