Also suffering from unexpected synchronisation errors as of this morning. Started with Beta 2, updated to Beta 4 and then again to Beta 5 with no improvement, Message: "1 error occurred: notebook is a required value" Coincidentally, I also had trouble with the automated updater and needed to download the binaries. Update: looking through the activity log, the sync error seems to be related to a publicly shared notebook. I'm fairly certain this is my only publicly shared notebook on my personal Evernote account. Have tried 'unsharing' but problem persists. Update 2: more an observation really. Skitch is still syncing. Presumably uses a different engine? Update 3: tried removing (renaming) the specific note that seemed to be the cause of the problems. No dice. Also tried resetting the SyncState file. Threw up a bunch of new errors with other notes/notebooks for some reason, and also didn't work.