Steve Bourne (yes, of Bourne Shell fame) interviewed Bruce Lindsay:
http://acmqueue.com/modules.php?name=Content&pa=showpage&pid=233
Particularly love the bit on “Heisenbugs”:
Heisenbug as originally defined—and I was there when it happened—are bugs in which clearly the behavior of the system is incorrect, and when you try to look to see why it’s incorrect, the problem goes away. Typically, when you are trying to see what’s incorrect, you turn on tracing or you add some more parameters or you change something. And the change causes the problem to go away. Quite often these problems occur because of concurrent executions. Or they occur because of the way the memory happened to get laid out in a particular case.
So the real definition of a Heisenbug is when you look, it goes away—in deference to Dr. [Werner] Heisenberg, who said, “The more closely you look at one thing, the less closely can you see something else.”