Suddenly on my Lemur UltraThin lemu1, the backlight is not turning
on, so when I boot I get a black screen. I can just barely
make out that the login box is displaying on the screen,
but it is essentially invisible without the backlight.
If I plug in an external screen or log on remotely,
the machine seems normal.

I am running Ubuntu 11.10 (oneiric ocelot) and have updated the
System76 drivers.
Using the function keys to change the brightness has no effect
on the laptop screen.

What can I do? Thanks.