Yesterday I did something really embarrassing considering I'm thought of as a 'computer expert' by everybody in the department.
My boss had opened up the Stat Mand laptop and proceeded to type the password (we have encrypted laptops in the NHS and only get 5 attempts).
She had failed so asked me to type the password and I failed 3 times

This was important because we needed this laptop for today where I would be facilitating 150 NHS staff on their Stat Mand Training so I called IT and told them it was priority.
It was getting late so we rang at 16:15 saying we need somebody now to get the laptop working so somebody was sent at 16:45.
I gave the IT man the password, he typed it in and it loaded

"What have you done?"
"I turned the Caps Lock key off"
Today (and I've done this twice now) I sent a member of staff back because they were over 15 minutes late for Stat Mand (they were 45 minutes late).
Later on I get a call from my Manager saying the bloke was a Consultant and in monetary terms it had cost an estimated £7,000 sending him back (you have to take into account the work he would have been doing today and the codes the Clinical Coders would put on his work).
My Managers backed me up with HR who also backed me up.