Re: "the thing just fell over,..it was computing a jump into the middle of a commented out section"
Ahhh. They just don't write code like that any more.
One of the big crash-landings we had when I was a programmer was writing self-modifying code. Since we were writing for an environment where a single code segment couldn't exceed 4K (and that had been raised from the original 1K), some of the previous generations had done some fairly aggressive things to keep their code small..
Like having self-modifying code. Which is fine when, in the old days, you only had a single thread to worry about and nothing would grab the CPU while your code was running, but by the time I got there, we had to code stuff so that it was re-entrant and could be used by multiple CPUs at once.
Which, of course, negated the advantage of self-modifying code since you could never guarentee how many CPUs were running your (single instance) code.
 Crash-landing was the term we cam e up for "if you do this it's an instant P45". Stuff like telling the CEO that he was an idiot..
 For a particularly difficult to maintain version of "fine". And trying to debug a core dump where the bit of code you are looking at doesn't match the source code isn't fun.