Some time ago, my mother bought a new laptop. It came preinstalled with Windows Vista, which proved to be quite the disaster. The laptop wasn't nowhere near fast enough to run it, so I installed Ubuntu on it. This allowed my mom to do everything she needed to do with the laptop, while at the same time making it easy for me to administer the beast.
One day my mom phoned me, and explained about a problem she was having:
"Whenever I move the laptop into the kitchen, it stops working!"
Now my mom is no computer expert, but she picked up Ubuntu quickly and has never needed much hand-holding when it comes to using the laptop. This one, however, sounded to me like one of those situations where the user couldn't possibly be correct. We went through the basic telephone support routine, but she persisted in her observation that somehow the kitchen was responsible for her laptop misery.
Eventually, after deciding the problem couldn't be fixed over the phone, I agreed to come over to my parents house the next evening to take a look at it. With my general moody "a family member's PC needs fixing" attitude and a healthy dose of skepticism ("this is going to be one of those typical the-cable-isn't-plugged-in problems"), I arrived at my parents.
"Okay, let's see if we can't fix this problem", I said, as I powered up the laptop upstairs. Everything worked fine. Picking up the laptop, I moved it downstairs into the living room. No problems whatsoever. Next, the kitchen. And lo and behold:
The laptop crashed almost immediately.
"Coincidence", I thought, and tried it again. And again, as soon as I entered the kitchen, the laptop crashed. I… was… Stunned! I had never encountered a problem like this before. What could possibly make it behave like that?
After pondering this strange problem for a while, I thought "what's the only location-dependent thing in a laptop?", and it dawned on me that it might just be related to the WiFi. I powered up the laptop once again in the living room, completely turned off the WiFi by rmmod-ing the relevant kernel modules, and entered the kitchen. No crash. It kept on working perfectly. Until I turned on the WiFi again.
With the aid of some log files (which I should have checked in the first place, I admit), I quickly found the culprit. The very last thing I saw in the log files just before the computer crashed… an attempt to discover the neighbors WiFi! A wonky WiFi router in combination with buggy drivers cause the laptop to crash, but only when it came in range of said WiFi router. And that happened only in the kitchen!
In the end I disabled automatic WiFi discovery on the laptop, since my mom didn't really take it out of the house anyway, and the problems disappeared. I never encountered a problem like that again, but I did learn one thing though:
No matter how impossible the problem may seem… The user isn't always wrong.