Writing scenes is definitely the right idea to really, really get started on this novel; but so is research. I'd forgotten that when I was stuck on the previous project, I would often return to my research materials, which inevitably struck off some new idea or connection. So now I'm reading one of the books I had piled up, and it's proved to be much more helpful than I'd imagined it would be, because it directly addresses some of the things I needed to know, in conjunction with its "real" topic. I've had whole new ideas for how my narrator got where she is, as opposed to the vague and unlikely idea of before. So now I can write scenes using those ideas.
My writing date with R. last Friday really helped. He reminded me that even if I didn't like what I'd written, it told me what wouldn't work.