Cleaners...
I was working on some documentation, around 250 pages, with images, written in Word 4.0 on a Mac Plus. I had finished the document and was going through putting in all the index markers. I was saving every 30 minutes or so, because it took the Mac an age to save such a large document. All was going fine, when the screen suddenly went dark.
The cleaner had come in behind me and just unplugged the nearest socket, the one with my Mac plugged into it. AAARRGGHH!!
Biting the hand that feeds IT
