1) Please confirm that you have worked through this lot - http://docs.moodle.org/22/en/Installation_FAQ#I_can.27t_log_in_-_I_just_stay_stuck_on_the_login_screen
2) Turn on Debugging (you'll probably need to do it in your config.php - see/copy section 8 in config-dist.php). What additional errors do you see? Check your web server error log too.
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