I've the same problem Ubuntu One don't want authenticate but :
I 've launched Tomboy and i've configured it for synchronizing with my UbuntuOne Account :
The OpenID's authentification process runs normally and the Tomboy Notes are synchronized with my UbuntuOne Account.
But UbuntuOne's Folder won't synchronize and i continue to have an infinite loop on authentication with UbunutOne Client every time i launch UbunutOne Client.
I've the same problem Ubuntu One don't want authenticate but :
I 've launched Tomboy and i've configured it for synchronizing with my UbuntuOne Account :
The OpenID's authentification process runs normally and the Tomboy Notes are synchronized with my UbuntuOne Account.
But UbuntuOne's Folder won't synchronize and i continue to have an infinite loop on authentication with UbunutOne Client every time i launch UbunutOne Client.