Login Password Problem

I'have just started to use Dolphin Community. It's perfect but there are some problems first problem was about security image but i solved it. It's okay now but there is another problem and it's about loging in I meant after you registered the website and try to log in site again it doesn't accept password (if your password is like smt like that "123asffad") but if your password consist of only numbers it's okay you can enter the website.

This is my problem i don't know how to solve this and this is important for my  members security because the password which is only contains numbers is not secure.

Best regards,
ProfessoR_X