Comment 27 for bug 674876

I solved or worked around the problem using this link:

https://wiki.ubuntu.com/UbuntuOne/Bugs

this section:

ROOT_MISMATCH in syncdaemon.log - This normally indicates that there may be two Ubuntu One accounts, one in the local cache and another setup in the keyring. This happens if the user installed Ubuntu One with one account and then sets up the computer again with a different account (but all the old Ubuntu One files in ~/.local/share/ubuntuone are still there under the old account). Working around this:

Open Applications->Accessories->Terminal and run:

  u1sdtool -q; killall ubuntuone-login ubuntuone-preferences;
  sudo rm -rf ~/.local/share/ubuntuone
  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:
  u1sdtool -q; killall ubuntuone-login; u1sdtool -c