I knew a guy who was a computer tech early in his career. One of his rounds was on a military base, and they had just moved their computer room up one floor. They started having problems with their tape drive, it would just randomly pop up an error while they were using it. He tried mightily to diagnose the problem but couldn't figure it out. Finally he took a break and walked to the nearest window and looked out. He saw a radar antenna making a sweep - and realized the error came when the antenna was pointed in their direction.