I'm not talking about the little applications you can download to sync up Facebook friend profile pictures with your AddressBook database. I'm talking about an app hidden in the Resources of the System Framework that's used to sync contacts between various devices, including the iPhone. Mine inexplicably went nuts recently and was crashing like crazy with every iPhone sync attempt. A Google search yielded practically nothing, so I knew I had a unique problem. I tried all the typical troubleshooting steps to no avail, including a deletion of preference files. So, here's what finally fixed it:
I used Pacifist to copy the System Framework called AddressBook onto my desktop from the 10.6.7 Combo Updater. I deleted the original in the /System/Frameworks/ folder and replaced with this one. I noticed that the AddressBookSync app was smaller in the Updater, so something obviously went wrong in the update process. After copying the new Framework into the proper location from my desktop, I repaired permissions and voila...no more crashes.