Ubuntu :: Cant Logout Without Black Screen Showing Up?

Every time me or another user uses the "log out" option were faced with a black screen that does not go away, unless the computer is restarted. i've left it for an hour thinking it might have just slowed down or something but that was a no go, and it happens each time you try to use it. the strange thing is if the black screen is up programs still run. i have a media server running most of the time and i have no problem accessing it while the black screen is showing.

Another problem im having is that sometimes when a user logs in they have no sound. the sound icon is showing that no sound is installed, but when another user logs in there is no problem and sound works fine.

Lastly i dont know if this is a feature or a problem. the first user to log in will always have control over the network connection. for example if my mother logs in first the icon to switch connections will show up on the top of her screen and she has full access to what connections she wants to use, also her account is just a basic user account. now when i log in i wont have the network icon on the top of my screen, and my account is the main admin account.