The problem has gone away overnight.
I have not touched the PMAC or PC since I posted yesterday and this morning it syncs to the database just fine. The PC hasn't rebooted, nor is it connected to the internet.
New problem:
All of the Add-Ins are now missing. If I select them in the menu, a message tells me that it cannot be located and asks me if I would like to remove it from the menu. I tried both the repair and the modify features of the PMAC Suite installer to try and re-install the addins, but it has not solved the problem.
Are these issues related?