A bit late to help the original poster, but perhaps for new googlers ...

I thought this morning that installing a new version of the intel video driver broke the ability for me to use the external VGA with a video projector. I was possibly wrong about that, but this is what I did to restore the previous driver:

> apt-cache show xserver-xorg-video-intel | fgrep Version:

From that I determined that the previous version was 2:2.9.0-1ubuntu2~xup~3

Reverted back to that one by doing:

> sudo apt-get install xserver-xorg-video-intel=2:2.9.0-1ubuntu2~xup~3

Hope that helps
cheers