I cann't add new role

Hallo Everyone: I have created a new role name accountant with few permissions, then I have added a new user with this new role. While this new user (with role accountant) try to log in error message comes with "403 Forbidden". After that, with several refresh, the error message doesn't go and login page don't load. Then I have to close the browser and re-load it again to work again. Can some one help me to solve the problem. Thanks