I had a problem where, after booting my Acer laptop I would get only a black screen. After some searching, I found out that the problem was that something shut off the backlight. It then took me a while to find information that I could actually understand but in the end I did find how to fix it. (Note: I’ve written this post as simple and in the most detail as I possibly could, to help users, like me, who are not so skilled in linux system administration)
To be honest, it is more of a workaround then a fix, but since not much seems to be happening in the bugreports… There are two parts: in the first part, we’ll fix it at boot time. To do so, open a terminal and sudo-open your favorite texteditor. (example: “sudo leafpad” or “sudo gedit”). When it opens, open the file “/etc/rc.local” (you can add that to the command to open the editor itself if you’d like). Normally, there is a whole bunch of comments (the lines starting with #) and then one line that says “exit 0″. Right above that line, type “sudo setpci -s 00:02.0 F4.B=00″. I’ve no clue as to what it does, but if you save that file and reboot your computer, you should see that it works (in my case, the backlight turned off, as it did before, but then turned on again a few seconds later).
The second part of the problem is to fix it so that when the screen resolution is changed, there is no problem. Again, it’s a bit of a stupid fix, and far from perfect, but it works. Again, open up your editor with sudo (as above, “sudo gedit” or something similar), but this time with a new file. Type in
#!/bin/bash
sudo setpci -s 00:02.0 F4.B=00
and save it in the /root directory (I named it fixbacklight.sh). Then, in your terminal, type “sudo chmod 0777 /root/fixbacklight.sh” (or whatever you named the file). Yes, I know giving 0777 permission to a file isn’t very save, but I didn’t want to bother searching the right permission. Then type in “sudo crontab -e”. This might ask you which editor you’d like, just type enter (it should suggest nano). If you haven’t used nano before, it might be a little difficult to use. Scroll to the bottom of the file with the down arrow and type in
* * * * * /root/fixbacklight.sh
Then use Ctrl+X to exit. It will ask you whether you want to save, type Y. Then it will ask you whereto, just type enter. Reboot and you should be ready. This, by the way, will execute that script (and thus turn on your backlight) every minute. It’s not perfect (as you might have to wait a while), but it does the job.
I hope this was of any use to someone 
.