Did you try increasing the screen brightness with the keyboard function? Happens to me too, but it's the brightness getting set to 0.

There was some switch around 9.10, different drivers or kernels or something. Here's what I used to get Lucid working on an old Gateway with a i915, it might work for you. http://ubuntu-tutorials.com/2010/05/06/ubuntu-10-04-lucid-bl...