In the various threads that all appear related to the recent password problem, there have been a couple of mentions of the coincidence that this seemed to occur at the same time as receipt of the suspicious 'Change of Terms of Service' email. This was indeed the same for me.
There has been a warning that the password could well have been hacked as well as corrupted.
I want to advise everyone that I have just discovered a fraudulent purchase on my Amazon account, which I am ashamed to say did share the same password. Just some music for a few quid, but it's definitely happened.
Anyone as careless as me, please be vigilant.