Cubase and Windows Power Management Problem

Have encountered an unusual situation on my Intel i7 Windows 7 Prof PC.

My machine was running well then for nor reason I can fathom started glitching on playing back audio online or offline in all apps ie MP3 played in Windows media player as one example. I had tested my machine with the DP latency checker and found where previously all was running in the green zone it was now glitching very badly. I tested all drivers with the methods suggested with the latency checker and found nothing. I checked BIOS and power management settings and nothing seemed to stop it. I then loaded Cubase and imported the same mp3 and found it played OK. Furthermore whilst Cubase (7.03) was running the mp3 file would play in media player OK. Online audio also streamed OK.

I then looked at the Cubase audio settings and discovered if I turned off the Steinberg power management setting all the audio playback glitching started again in both Cubase and all other audio playback process such as Windows media player and online streaming. I have concluded that my problem is therefore linked to Windows 7 Power management. When Cubase is running its Power Management Plan is visible under Win 7 Control Panel Power management dialogue.
So I then copied all the Steinberg Power Plan settings to a new plan.

I shut down Cubase and switched on the identical Power management plan. However nothing happened all the audio glitching remained.

The only way I can currently stop this glitching is to load Cubase 7.

I’ve no idea what the Cubase application is doing in replacing the Windows power management processes whilst it is running. The Steinberg programmers would know but they’re probably not using this forum.

If anyone has any ideas or comments on why this might be happening it would be appreciated.