Hi all!
Warning, a newbie here! 
This is version 12.1 with xfce. The problem is - monitor never powers off, never sleeps - after a few minutes it shows ‘blank screen’ (screen saver) and that is all.
Note, this command does not work: xset dpms force off
Note: # lspci -nn
00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 02)
Note: The best match I found with 11.4 is here: openSUSE 11.4: VGA monitor doesn’t go into standby - he solved it by installing ‘intel legacy’ drivers - these are already installed on my system.
BTW I didn’t try vbetools.
The problem you are having is the exact opposite of what I was having. I didn’t want power turned off on my monitor. I only wanted the screen saver to kick in after 10 minutes of inactivity. But nothing seem to work for me. I learned that there is a power managment appilcation for Yast2, and I just used the default options. There are other options that can be used for your situation. But this took care of my problem and maybe it can take care of yours. Hope this helps.
I am having the exact same problem, except that I am using KDE. I am on the intel legacy drivers just as he is. I would appreciate it if anyone has input.
Hello Kiyohime, have you solved it, yet? I have this very issue. Different video card though!
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07)
00:02.1 Display controller [0380]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a43] (rev 07)