If a user uses caps lock instead of shift, I immediately assume they're the reason their password doesn't work.
Don't get me wrong, I wish all heathen Caps Lockers happy and full lives, but in every single password failure instance I've had where I've noticed the user using caps lock in place of the shift key, it has resulted in them making a typo and their password failing. And when they blame the system, I suggest a generic password to test, and it immediately works.
Thanks for letting me rant, I needed that.