PhpBB setup

This is a VERY simple project. I successfully set up and instaleld a phpBB Forum. HOWEVER, when registered users go to the Forum they enter a password that works then it loops them into their account where they are asked for their password again when they go to the Forum. It asks them for the password again and they use the same PW but it fails. The other test user I put on has no problem. I am sure that this is either soemthing I did not set right or I do not know how to approve and get new users onto the system,. Either way it is simple and should not require any programming.