Poser cuts the mesh into pieces so in order to use LW morphs you have to do the following:
Freeze the subpatched model to polygons,
Export the endomorph model exactly the way you do the original,
Load the endomorph model into Poser exactly the same way you do the original,
Now export the morphed parts from Poser as objs and re-import as morph targets.

This is how you Have to do it to overcome Poser's slicing and dicing the mesh.
When you export just the head from LW, you end up with a different vertex order than when you export the head from Poser; different vertex order results in the morph blowing up.

BTW, In LW you pretty much have to subpatch to get a smooth render whereas POser has a rendertime setting that does subpatch smoothing for the render (about the only positive thing I have to say about Poser LOL).