Don't know about most painful, but it definitely sticks out.

My mother screamed for me at the top of her lungs on the other side of the apartment. I hurried into her office, where I see her pointing at the screen saying "FIX IT!" So I look at the screen and... it's a save dialogue in Word, asking her if she wants to save her document.

Me: It's asking you if you want to save the document.
Mother: Well how am I supposed to know that?
Me: Do you want to save the document?
M: I DON'T KNOW!!

It's like she saw the dialogue and her brain crashed. She definitely could've read and understood it, but just chose not to. That sort of thing was a frequent occurrence sadly.