Windows XP Home – hibernation.

I have put my desktop PC into Suspend -> hibernation many times, without mishap. Last night, however, I did the same – and moving the mouse and/or tapping the spacebar has no effect. Reset or restart has no effect, i.e. blank screen with just the system and HDD lights lit. PC will not boot, either from diskette, recovery CD nor obviously from HDD. Does anyone have any ideas how I might “wake up” the PC?