Ein wunderbares Wort, das ein grosses Problem der Software-Entwicklung beschreibt (Quelle: Wikipedia):
A heisenbug (named after the Heisenberg Uncertainty Principle) is a computer bug that disappears or alters its characteristics when an attempt is made to study it.
The name heisenbug is a pun on the Heisenberg uncertainty principle, a quantum physics concept which is commonly (yet inaccurately) used to refer to the fact that in the Copenhagen Interpretation model of quantum mechanical behaviour, observers affect what they are observing, by the mere act of observing it alone (this is actually the observer effect, and is commonly confused with the Heisenberg uncertainty principle).