Open Applications->Accessories->Terminal and run:
rm -rf ~/.cache/ubuntuone
rm -rf ~/.config/ubuntuone
mv ~/Ubuntu\ One/ ~/Ubuntu\ One_old/
Open Applications->Accessories->Passwords and Encryption Keys, go to the Passwords tab, delete the Ubuntu One and Desktopcouch tokens by right-clicking on them and selecting «Delete»
Back in a terminal session, run:
After doing all this syncing notes with tomboy still won’t work until you make tomboy re-authentificate with ubuntuone (see the tomboy section of this page).