Sandi, I can see exactly what you are saying - and can see it happening in real time here in my own sitch. Although my W has completely denied it the few times I (in a moment of DAMness) brought it up, I know (and have seen evidence) that my W is still fantasizing about OM. He's the white knight, and I am the barrier (or the ogre, to keep the analogy going) that is separating her from happiness.
All of which leaves the LBS with a very tough question - "How do you compete with a secret fantasy?" Answer: "You can't!"
Me 42, W 39, S8, S6, S2 M 11y, A & ILYBNILWY 11/08 Walking away from a bad situation.