I have the same problem on my Dell D820. "xset dpms force off" shuts down the backlight, but it comes back on after a couple of seconds. This has been reported on the forums as well: http://ubuntuforums.org/showthread.php?p=8337312#post8337312
Same bug is found here: http://superuser.com/questions/66918/suspend-screen-command-in-ubuntu-9-10-gnome
And a bug has been issued on Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=552506 .
I have the same problem on my Dell D820. "xset dpms force off" shuts down the backlight, but it comes back on after a couple of seconds. This has been reported on the forums as well: http:// ubuntuforums. org/showthread. php?p=8337312# post8337312
Same bug is found here: http:// superuser. com/questions/ 66918/suspend- screen- command- in-ubuntu- 9-10-gnome
And a bug has been issued on Debian: http:// bugs.debian. org/cgi- bin/bugreport. cgi?bug= 552506 .