The one thing that springs to mind is lighting the bump map in a 2D application. Especially because you want to change just a part of the bumps. But, another thing can be that the deepness of the bumps stands out more because it is such an articulate relatively small, round part of the face. So you bump map is too strong everywhere. Then you could just change the bump height in the shader. Good luck! (I am now in contact with Carrara Support about no texture maps at all in OSX with Poser 4, so I can not try out the situation, yet)