There is a common issue with Intel graphics resulting in screen resolutions not being available even after adding them to the xorg.conf file. This happens with the i810 video driver, but the newer intel driver does not have this problem.

Install newer modesetting Intel video driver

Unfortunately the newer driver is only available from 6.10 onwards (Edgy, Feisty etc), but not in 6.06.1 (Dapper). If you have Edgy or above then you can install the newer intel video driver with:-

sudo apt-get install xserver-xorg-video-intel 

Then edit your /etc/X11/xorg.conf and change the

Driver "i810" 

to

Driver "intel"