uhmm... I had messy OBJs import and hang in Poser before.  I had to clean them up by running them through MeshLab, for example.  The resulting geometry could be imported.

Imported meshes which cause Poser to hang, could have overlapping vertices or intersecting polygons.  Or facets removed from surfaces, or edges without facets, and so on.  Sometimes, these occur at such a small scale that visual inspection alone cannot identify the problems.  

Eternal Hobbyist