A lot of the lights can cause lock ups. You need to change all lights to the ray trace setting, not the other one. (Sorry, I'm not at a Posered computer right now.) I've had problems with MAT files sometimes not working. P5 just decides I've changed my mind enough times and refuses to apply MAT files some times. Don't know why. P5 has severe hissy fits if it can't find a texture. You might be able to get it to recover, but it's a crap shoot. I'm in the habit of saving files before using textures or MAT files, just in case. Good luck!