iphone 3gs contacts not syncing but groups show. what gives?

I have an iPhone 3gs (software v 4.3.3) and itunes 10.2.2 on a macbook. I cannot sync my contacts to/from the mac. all contacts are still in Address book, and the address book contact groups show up on my iphone when I sink, but there's nothing in the groups on the iphone after the sync. syncing to/from ical works fine as does other sync functions. i've even tried an entire restore and this did not fix the problem.

Help!

I haven't seen this particular problem so I'm asking if anyone knows of a cure.

Thanks!