There's a pivotal plot point in Stranger that I've been uncomfortable with for a while. It was obvious to me that I needed to alter it, but I couldn't quite figure out how. This morning I woke up about 7:30 and stared at the ceiling for a while, so as not to wake up DH, and suddenly it came to me precisely how I needed to rewrite Stranger in order to fix the problem. One scene will have to be totally rewritten, and a few others altered slightly, but as a result the whole book will be much stronger and more logical.
It's odd... writing is very definitely a subconscious activity for me. I suddenly get ideas when I'm just going to sleep, just waking up, or taking a walk and letting my mind wander. I can't always force a story to cooperate, but sooner or later the answers to problems well up out of the dark recesses of my brain. This is part of the reason that I'm not generally a terribly fast writer-- my subconsious is on its own timetable!