Helen Keller mode

heisenbug = H = Hello Sailor!

Helen Keller mode n.

1. State of a hardware or software system that is deaf, dumb, and blind, i.e., accepting no input and generating no output, usually due to an infinite loop or some other excursion into deep space. (Unfair to the real Helen Keller, whose success at learning speech was triumphant.) See also go flatline, catatonic.
2. On IBM PCs under DOS, refers to a specific failure mode in which a screen saver has kicked in over an ill-behaved application which bypasses the very interrupts the screen saver watches for activity. Your choices are to try to get from the program's current state through a successful save-and-exit without being able to see what you're doing, or to re-boot the machine. This isn't (strictly speaking) a crash.

--The Jargon File version 4.3.3, ed. ESR, previously autonoded by rescdsk.