I am having similar issues on Xubuntu 12.10. Everything worked perfectly on earlier versions of Xubuntu. Now, no matter what I do, xscreensaver will not allow the monitor to power off. In fact, if I run "xflock4;;xset dpms force off" the monitor powers off, and gets woken back up5-10 seconds later! If I run "xset dpms force off" without xscreensaver, the monitor stays off. xscreensaver is obviously preventing my screen from staying off.
I am having similar issues on Xubuntu 12.10. Everything worked perfectly on earlier versions of Xubuntu. Now, no matter what I do, xscreensaver will not allow the monitor to power off. In fact, if I run "xflock4;;xset dpms force off" the monitor powers off, and gets woken back up5-10 seconds later! If I run "xset dpms force off" without xscreensaver, the monitor stays off. xscreensaver is obviously preventing my screen from staying off.