Well for the sleep and hibernate I would normally suspect the OS sending some wakeup call. Would happen quite usually with Vista. Not sure of the current state of Windows. Could happen on linux too wit messed up cron. But you said that it also powers up from a shutdowned state. If it happened then and still persists, following common knowledge it has to be one of the remaining components. The case usually has nothing to do with the computers operation. If the csse itself though has some wires, you can try to leave them unplugged. It should only effect some lights, But you never know. If the GPUs are the same. You can try to unplug then too and see if the problem is still there. If yes, then it somehow just simply has to be the psu sending some random switch on events. Could be that it turns itself on and the rest of the computer thinks it as a pushed power button. Tha is just a wild quess but what combination of solutipns are there