Help! I am currently stuck in the user authentication.

Hello,
I use FreeRadius +coovaAp+mysql +Drapal hotspot .
I am currently stuck in the user authentication. everything is ok while the Drapal hotspot is used "Auto Login as the user defined below". but, the user can't be authenticated while user authentication is used "User login form",. Ofcouse, the username and passwd is same.

How is it possible ?

Everybody Help!!