Flexible/inflexible

Every now and then, Julie will come out with something truly paradoxical. If you look at each word and even (sometimes) some basic elements of what has been said, they will make perfect sense. It's only when you put it all together, look at it as a whole and compare it with what you know of the situation and of Julie that it becomes a real Derailment.*

See? Everything's going tickety-boo and then along comes that final phrase and suddenly you find your brain has gone all BSOD.**

*So called because a random comment from Julie can do to your thought processes what a tree-trunk across a line can do to a speeding locomotive.

**BSOD Blue Screen Of Death - massive PC failure for non-techies and smug Apple owners.