Comment 6 for bug 356766

I have this same problem in Lucid and I don't find this bug to be spurious, it always happens if you try to change only the last characters of your password.

By the way, let me add that when you try to change your password through the Ubuntu user interface (System -> Preferences -> About me -> Change password) it will never end the task (I think that the error message should be displayed or at least end in some way).