To kick off my error message “hall of shame” series, I thought I should share my all-time favorite. I got this one many years ago, I was minding my own business and suddenly this pops up in the middle of my screen:

I did not have the presence of mind to take a screenshot back then, so this is “faked” from memory, but all the essentials are here: An empty title bar, so I have no idea which program generated the error, the “unknown error” deepens the mystery and the “ok” button serves as a cruel, taunting punchline.

I never figured out which program issued this error, everything seemed to continue normally. Great mysteries, indeed.