If I may also add. I once had trouble getting my password to reset after upgrading to a new version... I would go to my admin panel where I was prompted to log in, but because of the upgrade, I couldn't. I tried entering the captcha, but it wouldn't work... that is until I discovered that the captcha is CaSe SeNsiTive!
So, basically.. go to where you usually log in, type in the case sensitive captcha into the password box and click the "Log In" button. Then check your e-mail associated with your ZenPhoto installation. You should get a link which will allow you to reset your password.
Hope that helps.