Hmmm ...
When you logout, what happens exactly? Do you see only a black screen, or do you see the nvidia splashscreen again (which would indicate that at least X has restarted) or maybe a text login or blinking cursor?
FWIW you could try to use another display manager, like KDM or SLIM or XDM or whatever, they can be easily switched after installation via drakx11:
http://doc.mageia.org/mcc/3/en/content/drakedm.html