I'm really not sure what it could be. Given that it's only affecting two members and no changes have been made to the site, I'd have to say it's a problem on the user end.
To confirm this you'd need to use someone else's computer or another browser. You can request a password reset automatically. Choose something memorable like a passphrase next time, or write it down somewhere secure.
To confirm this you'd need to use someone else's computer or another browser. You can request a password reset automatically. Choose something memorable like a passphrase next time, or write it down somewhere secure.