Here is what might be going on. Are you by any chance modifying the texture while poser is still open, and with the same scene? I've found that poser is lazy, and won't reload textures just because you changed the texture file. You can force it to reload by closing the scene and then re-opening it. I'm not sure whether this is still a problem in P7, but i suspect that it is if you are using textured shading in the preview.