Keyboard/Mouse stop working randomly

I was taking care of some viruses for a co-worker of mine, and saw a problem that he didn't tell me about. The mouse and keyboard randomly stop functioning, although the light on the optical mouse and the num lock light stays on on the keyboard (so it still has power). This problem is easily remedied by a reboot... for a while, and then it happens again. I gave up trying to fix it and just reformatted. After successfully installing a few programs back onto his computer, the exact same thing started happening again. It's unlikely that it's a virus causing this since I reformatted... right? What else could it be?

Jam it back in, in the dark.

Originally Posted by Shin

Silly question perhaps but are they wireless? It could be the batteries running out...

Neither the keyboard or the mouse are wireless.

Originally Posted by Zergrinch

Sounds like a hardware problem. It can either be a failing (or as Shin said, unpowered) keyboard/mouse. It can also be a flaky motherboard, causing the USB or PS/2 ports to sporadically fail.

The keyboard is PS/2, and the Mouse is USB 2.0. Neither power off, and they both stop functioning at the same time. You'd think the screen would power off too since it is an integrated graphics card if it were a flaky motherboard, but I can't think of any other theory.

There's nowhere I can't reach.

Originally Posted by Zergrinch

DeLorean, I have experienced a simultaneous mouse/keyboard KO before. It's when a USB device was drawing too much power is switched on. In my case, connecting a gold plated USB cable to any USB port, powered or not, does this with 100% certainty.

My advice now is to disconnect every single USB device, and see if this happens still.

That makes sense because I noticed that the power supply has very low wattage. I'll test it when I get home. Thanks for the replies.

This thing is sticky, and I don't like it. I don't appreciate it.