Just curious, if it's a subd object, why even bother convert to poly? Just map the subd object. The general rule is that you should be texturing when the final object is completely modeled so I would think converting textured objects back and forth is going to throw something off, in this case, maybe it's the bump map. That being said, I would try either converting it to poly and doing all the mapping to that...or just map it all as subd. Try it and see if you get the same problems.