Seems like everyone else has covered the basics.  Your workflow was correct, but your modeler was changing vertex order -- one of the three major things that can go wrong when making morphs in an external modeler (the other biggie to watch out for is modelers that change the size on import or change the location in object space.  You will know when this happens, as the morph will cause the object to either inflate wildly or go shooting off in some direction or other).

For very simple morphs, it is often faster to apply a magnet inside Poser itself, and save that result (aka "spawn morph target.")  I use a combination of both, myself, for the things I build.