When I added loopbacks, I actually had to reload the router to get it to take the loopback IP as the router ID. SH IP OSPF NEI on a nearby router should tell you how this router is known to the rest of the world.
I have to admit, I went right to reloading the router. I figured that trying to figure it out instead of just fixing it was more an acedemic exercise. When a warm supper is at home, I generally shy away from acedemics!