Called Sony tech support. He confirms that 64-bit snow leopard is not compatible with the reader software. They are getting complaints and requests for an update to the software since Snow Leopard is becoming more prevalent among the Mac population. For now, starting the OS in 32-bit mode (2 and 3 together on bootup?) is a workaround, or going to a 32-bit computer to perform the sync.
Sorry the news couldn't be better, but it sure saves some time don't it?
ETA: yes, this fixes the problem. If you can afford to restart your Mac in 32-bit mode, go ahead and do that then sync your device with the new books. Many times the 64-bit mode isn't really all that noticeable. In any event, you can always restart in 64-bit mode once you're done syncing. Hopefully they'll find a fix for this in a future version.