I read your post carefully for the machine details but came up short. Try this. Reinstall the OS and add your stuff one by one until it breaks. Next time skip the item or setting that breaks this feature.
I set my monitor to shut down minutes after the screensaver activates but once the monitor goes to shut off it goes through the motions but does not power down. This occurs with any screensaver I try. I've researced on the internet to no avail. When Im not running screensaver the monitor shuts down with no problem. I even tried the power settings in Manage. Nothing. Please help. thx in advance.