My laptop is Dell Inspiron 1505, with ATI Mobility Card
When i installed Ubuntu Feisty X-Server was not starting. Instructions to fix:
sudo apt-get update
sudo apt-get install linux-restricted-modules-$(uname -r)
sudo apt-get install xorg-driver-fglrx
sudo depmod -a
After that reconfigure X Server
sudo dpkg-reconfigure xserver-xorg
Select fglx driver, keep remaining all default settings(for keyboard etc). Do not auto detect monitor (this hangs on my system)
After you done with reconfiguring restart your xserver or just reboot your machine.
To fix resolution problem: