After going through an upgrade from 7.0 to 7.1, my DPMS screen blanking stopped working. I do an "xset dpms 600 1200 1800" then leave the system. When I return, I used to see a blanked screen, but now I find the xscreensaver graphic hack running and "xset q" shows that DPMS is disabled! I did some experiments and found that turning off xscreensaver fixes the problem - i.e. it appears that xscreensaver is disabling DPMS. I finally settled on the workaround of falling back to xscreensaver-3.25-4 from RedHat 7.0. So, the problem seems to have been introduced somewhere between there and xscreensaver-3.29-3 from 7.1
xscreensaver now handles DPMS settings; you can configure it with xscreensaver-demo, or via command-line arguments in the forthcoming xscreensaver-3.32-1 package.
*** Bug 41990 has been marked as a duplicate of this bug. ***