I can think of very few scenarios that would send me into an 8 hour fury and caffeine fueled debug session as quickly as that.

It's one of those problems that throws you into a fit of self doubt and paranoia. You question your basic assumptions, your hardware, your colleagues, and God himself before making any headway and it turns out its often someone else's "fault", who programmed some core feature of a library 25 years ago in an obscure way, because they never could have imagined the Frankenstein-esque behemoth their code would be embedded in nearly 3 decades later.