"Required file cannot be found" when syncing photos

I'm getting the "The iPad "iPad" cannot be synced. The required file cannot be found" when syncing my photos. Everything else seems to sync successfully. I was able to sync my photos a couple of times until I started to delete some photos, change album names, move pics around in albums and merge/rename events. I've emptied my trash to get rid of the deleted photos.

When the library does seem to "update" on the iPad, I have some seemingly empty spots on Faces where I've deleted photos from the original photo sync-- if I touch there, the old name comes but the photo is gone.