Hi, I just purchased a Mac Pro 8c, 2.4ghz 3 weeks ago. On a rare occasion I hear a electronic crackling or popping sound from the computer. I was leaving the computer alone for awhile and heard a moderate crackling/popping sound from the front. I thought it might be someone using a cellphone nearby? I also sometimes hold down letters on the keyboard for about 5 secs and hear the sound from the back of the computer? Sounds like it's coming from the speakers? Anyone else?