I have had similar problems. I haven't tried many mat poses, so I'm not sure how they are supposed to work, I guess. This is what happened to me. When I applied the mat pose, the body parts that were effected were listed under the Render/Materials/Object list under the figure. So besides having Figure 1 (in the Render/Materials/Objects list) with skin, etc in the Render/Materials/Material list; I also had Hip, Thigh, Shin, etc (in the Render/Materials/Objects list) each with all of the materials (like skin, etc) in the Render/Materials/Material list. Changing texture for the Figure no longer had any effect. I had to change it for each body part that now appeared in the Object list. This isn't really a solution, but it may be what happened to you customer. I hope this helps a little. It's a bit hard to describe. Ericroy