It seems that some service or program is preventing my monitor from going into power save mode but I cannot find a way to dig down the cause.

Does anybody know a way to find out which event may be causing the problem?

Background information:
If I leave/lock my computer I want to immediately power off the monitor.
Stupid windows has no program for this so I use a third party utility.
I use Display.exe from Noel Danjou since 2005 and have had no problem with it on XP, my Notebook with w7 x64 pro and at the office with w7 x64 enterprise.
With my new home pc with w7 x64 pro the monitor goes off but instantly comes back on after a second.
So I tested using a power plan with the shortest timeout of 1 minute but with that the display never goes off at all.
(Setting a power plan timeout is no useful option because then I cannot read a document or watch a movie without the monitor going off)

I could try trial and error methods but this is cumbersome and not what I regard as a professional solution.
So I would prefer a way to analyze the windows events to find out the reason for the display staying active.

Add On:
In the meantime I tried safe mode and also exited from all tray programs but the problem is still there.
I also checked the BIOS for special power settings but still no solution (P.S. Mobo is H87-G41 PC Mate with latest BIOS rev.)