Hmm. Maybe. I had a similar thing with Google Sync. Go to your mobile me preferances, and if it is anything like exchange ( never tried mobile me) de-select contacts, then reselect it, and when it asks you to keep or replace contacts. Click replace. See if that does the trick
It's because you have MobileMe turned on in your phone to sync you contacts and then you have iTunes set up to sync with your address book. Turn off syncing with your address book in iTunes and you should be set.