The first synch I made with beta11 was uploading a 120Mb file. The file uploaded correctly too, but when the player had to restart I got an error and the player locked up. Don't know if it's the same error you guys had, but I suspect it is.
Manually cold rebooting the player did the trick. I didn't even have to resynch to rebuild the database. All continued like nothing had happened.

All my other synchs I've tried since then have been successful.