ubuntu 14.04 login password reentering problem

When i start to OS, enter the password, and в little бит second, it want to enter password again. If i enter wrong password, it warn я to invalid password, but i enter right password, it stay to want password.

Заметьте: it happens after i install nvidia драйвер manually. i follow the instruction below видео: https://www.youtube.com/watch? v=pZ-r3gS38RU

i stop the lightdm service while installing драйвер? хан it вызвал this ошибку?