I had a sudden brainstorm and deleted the problem note on the PC, recreated it and then went to my tablet and it synced immediately and properly. It makes no sense whatsoever, given the error message that was received, but it worked. So I'm thinking the error message was just rather generic and just told me there was a problem syncing without telling me that the problem had something to do with the one particular file. All is well now. Hope it stays that way.
I am having the same problem on my Samsung tablet. It synced yesterday with no problem. Today I added a new note on my PC but it did not sync to my tablet. It says the sync failed due to an authentication error. Hoping someone can help.