I've been running WordPress Sites for years, and have never had this happen before.
Today, I went to login to a 3.9.1 site I run over on DigitalOcean. I login to it about every other day. Today it wouldn't accept my password for admin (admin username was changed to something else for security , if that matters)
Anyway, I used the reset password function and reset the password and everything seems back to normal. poking around the server, I don't see any obvious signs of being hacked.
What could cause my password to become invalid? (Other than disk corruption)
This is very strange, and somewhat concerning to me.