In one of my desktop installations (12.04), U1 perpetually says syncronizing but never finishes. It receives new files that are uploaded in other computers but it does not upload files that I place in the folder locally.
I have tried deleting the cache, the config files and redoing everything but is not solved.
I do not see any useful information in the logs either.
I do not notice anythhing wrong in nautilus or anything else.