Stand By

On average one out of eight times I put my PC in Stand By I cannot get it back. When I touch the keyboard or move the mouse I heard the hard drive start, but that’s all. The keyboard then locks. No video, no USB, and no mouse. The only way to get the PC back is to power down/up.
Thinking it was some software I was using, I started shutting down each program before going to Stand By. What a pain. To no avail. Still locks now and then.
Any suggestions? Tom