Ubuntu 10.04 does not recognize the display settings on a Lenovo X220 with an intel graphics card. I was not able to set the correct screen resolution or get the second display to work.

Have a look at this post:
http://ubuntuforums.org/showthread.php?t=1820722

The following line did the magic for me:
sudo apt-get install linux-image-generic-lts-backport-natty linux-headers-generic-lts-backport-natty