The new Ubuntu 11.10 Oneiric is bringing many problems for many users, the best known are the file manager Nautilus that closes for no reason, the Grub bootloader is not visible and 'inability to install deb packages with Ubuntu Software Center and now there's also problems with new Desktop Manager LightDm.
The new LightDm in my opinion is an example of the new release Ubuntu ie a new project beautiful to look at how unstable, In fact, many users report the inability to enter the password when you log on ending the session, Display Problems and even some blocks during startup of Gnome Shell and Gnome Classic blocking the OS to the point that we must proceed with the much "loved" reset button of our PC.
How to solve this problem?
If we do not want to wait for the team Canonical solve problems LightDm the only thing to do is change Desktop Manager the is more suitable GDM stabilissimo but not customizable (and who cares!) created their own team Gnome and default on Ubuntu up to 11.10.
Install GDM and set it as Desktop Manager default of Ubuntu 11.10 is very simple, simply start the terminal and type:
sudo apt-get install gdm
During the installation will appear in our terminal with a screen that will show us to confirm the inclusion of our new Desktop Manager and set the default to do this we select the first screen by clicking OK on the Tab key and press Enter.
Now we will be asked to indicate which Desktop Manager to use (Image below) with the arrow keys to choose gdm and click on Sending.
At the end we will have to restart our new Desktop Manager GDM fully functional and stable.
If we are to regain LightDM as the default Desktop Manager Just launch a terminal and type;
sudo dpkg-reconfigure lightdm
and choose LightDM.