Heisenbugs, Schroedinbugs

I'm horrified that I hadn't come across these concept/terms before. From the Free On-Line Dictionary of Computing:

Heisenbug: (From Heisenberg's Uncertainty Principle in quantum physics) A bug that disappears or alters its behaviour when one attempts to probe or isolate it. (This usage is not even particularly fanciful; the use of a debugger sometimes alters a program's operating environment significantly enough that buggy code, such as that which relies on the values of uninitialised memory, behaves quite differently.)

Schroedinbug: (MIT, from the Schroedinger's Cat thought-experiment in quantum physics) A design or implementation bug in a program that doesn't manifest until someone reading source or using the program in an unusual way notices that it never should have worked, at which point the program promptly stops working for everybody until fixed. Though (like bit rot) this sounds impossible, it happens; some programs have harboured latent schroedinbugs for years.

Follow the links for more related terms.