I run a wined version of steam (mostly because most of my steam games aren't avaible on the steam beta yet) and I had problems in the past with this black screen/dim screen but I fixed it, the problem is that whenever I try to run a game in full screen mode, the screen goes extremly dark again [can still hear sounds and see a few bright parts, especially with a lamp turned on]. I don't want to play games in a small window forever, but I don't want to go back to windows either.
Information: acer aspire 5732Z [laptop], intel pentium processor t4400 (2.2GHz, 800 MHz FSB), intel GMA 4500M, 2GB ram, 250 GB HDD
I had same problem when I installed ubuntu (11.10) first time on my laptop, I fixed it with the command sudo setpci -s 00:02.0 F4.B=01
after that I used gksudo gedit /etc/rc.local
and added the setpci -s 00:02.0 F4.B=01 after exit 0.