Comment 1 for bug 406897

I found a solution here: https://bugs.launchpad.net/ubuntuone-client/+bug/363243

I also removed the Ubuntu One entry (/token) from Seahorse (Passwords and Encryption Keys, 'Passwords' tab), uninstalled Ubuntu One packages including configuration, followed the Installation manual in the Web client and I was able to add my computer again after disabling NoScript in Firefox.

I think that the token should be removed with the configuration of one of the Ubuntu One client packages, though. Maybe it was already mentioned, Im not sure.