It still seems to sync most things - the error occurs late in the sync toward the end of the last step, which seems to be photo-related, and my apps are up to date, etc.
The main thing I've noticed that's off is my pictures - when I open the pictures app, I get a message saying:
iTunes Sync Needed - High Resolution images synced via itunes are missing. Connect your device to the computer you sync photos from and launch iTunes to sync them.
Since the issue seems like it might be photo-related, I tried repairing my Aperture library's permissions and database - no help.