I changed all of my Yahoo email passwords yesterday after learning that they had been hacked. I checked, and none of my accounts were compromised, but I changed the passwords anyway. Yahoo's email system accepted my changes, and it was business as usual.
As of this evening, none of my Yahoo accounts are letting me log in with the new passwords. This is after Yahoo Email said my passwords had been successfully changed more than 24 hours earlier.
I was able to log in with the old ones. WTF?
Yahoo has 24 hours to fix this problem, or I switch to another host.