one of the two fans on top of my case directly above my CPU cooler is making noises...sounds like it's grinding against sand. I thought a wire is touching it but there are no wires near it. As i put my hands in between the fan and the CPU i felt "tingly" pinches around my hands...maybe electirc problems? what can is be? no other fans produce this sound and "shocks" me...so i turned it off for now...is this a serious problem?