I import all my Poser stuff through Bryce 5 so that I don't get the grouping by material.  I go through the model then picking out what I want to group together and texture differently.  Then I open the scene again in Bryce 5.5 and go on from there.   It's fiddly but say with Noggin's raven, I really like being able to put different touches of blue, purple and green specular highlights on different parts of his plumage.  Simply ungrouping hasn't worked for me in these situations because the mesh seems permanently welded together in the new setting and may appear as only two parts for instance rather than about twenty or more if I take it through Bryce 5.