There is a story that goes around UNSW about how a large computer was having constant single bit errors. Every part was replaced but it still kept happening. Eventually, someone realised that the radar tower at the nearby Sydney airport used to sweep directly over the top floor of that building, inducing the errors; a Faraday cage was installed and all was well.
Today I read another interesting problem that came from outside the box; Rob Fowler from Rice University wrote :
I've recently had discussions with several vendors who have mentioned similar magnitudes of disk performance degradation due to the coupling of vibration between cooling fans and disks. This can dramatically increase seek time by keeping the arm from settling. In one case, upgrading a chassis fan caused disk throughput to go down by a factor of 16. The solution is careful attention to vibration damping in mountings.
When you have a problem think outside the box, literally!