I recently installed a new Antec 550w hard drive as an upgrade over a OCZ 500w. When it was first turned on, everything turned on and worked fine. But the second time, everything would turn on, but the motherboard wouldn't POST and the monitor would recieve no signal. i wiggled some cables, and got it to turn on, but then in the middle of a youtube video it froze and the monitor signal went away. Everything sounded as if it was still running. What could the issue be?