Updated from 11.10 to 12.04 after fresh install, often the lock screen will give me a black screen with a mouse cursor instead of the usual. This occurs most often while the Ubuntu software center is open or left unattended for a long period of time.

I have a mouse cursor I can move and even select the area where I would enter my password. If typed in and I press enter I can no longer select the text area like it logged in, yet still have a black screen.

I can enter the terminal and the Ctrl+Alt+Del to restart the computer in order to get back in. Is there any fix for this or a way to get back to the GUI without restarting the whole computer?