[_cereal]

Sounds like a schroedinbug:

http://catb.org/jargon/html/S/schroedinbug.html

[lokedhs]

If someone had not heard of that one before, it should not be confused with a Heisenbug, which is approximately the opposite thing.

http://catb.org/jargon/html/H/heisenbug.html