Unusual code bugs
I've been reading wikipedia article about [unusual bugs][1]. I'm particularly intereted in:

    Schrödinbug

A schrödinbug is a bug that manifests only after someone reading source code or using the program in an unusual way notices that it never should have worked in the first place, at which point the program promptly stops working for everybody until fixed. The Jargon File adds: "Though... this sounds impossible, it happens; some programs have harbored latent schrödinbugs for years."

and in 

    Heisenbug
    
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.



Does anyone encountered such a tricky bugs in his code? Can you provide with some real life examples?

  [1]: http://en.wikipedia.org/wiki/Unusual_software_bug
Unusual code bugs
===

I've been reading wikipedia article about [unusual bugs][1]. I'm particularly intereted in:

    Schrödinbug

A schrödinbug is a bug that manifests only after someone reading source code or using the program in an unusual way notices that it never should have worked in the first place, at which point the program promptly stops working for everybody until fixed. The Jargon File adds: "Though... this sounds impossible, it happens; some programs have harbored latent schrödinbugs for years."

and in 

    Heisenbug
    
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.



Does anyone encountered such a tricky bugs in his code? Can you provide with some real life examples?

  [1]: http://en.wikipedia.org/wiki/Unusual_software_bug