Moving day
I scheduled a vacation day for moving from a rental to our first house (it came with a mortgage :P). Unfortunately, our rental was within easy walking distance from work and the morning of the move, my supervisor came knocking, saying the Internet was down. Turned out my senior (age-wise) colleague who was supposed to act as my backup didn't know the difference between power-cycling and hard resetting a router/gateway/firewall. Sigh... Thankfully, I had a recent backup of the router configuration, so it was a relatively minor distraction.
By the way, this is not a case where the backup "technician" became one by default/accident. This person has a graduate-level computer-related degree.
