In message 01cd1ce7$ef07c7a0$LocalHost@default, at 22:33:37 on Tue, 17
Apr 2012, Michael R N Dolbear remarked:
If it was just a glitch, I may remark that in my thirty years as a
System programmer I proved the existence of a hardware error (that
didn't crash the system) precisely twice.

Software errors are far more common, however.
--
Roland Perry