This doesn't seem to affect all accounts (I am able to login just fine), but some accounts seem to have issues logging in since today on mediawiki.org, and 1.24wmf16 was deployed yesterday. This can't be just a coincidence.
[b596cdd3] 2014-08-01 09:04:31: Fatal exception of type PasswordError
[979b6eb4] 2014-08-01 12:49:06: Fatal exception of type PasswordError
See URL for those reports.