Thanks for your report Marianne. It seems that the reversed() function is only in Python 2.4 and the latest version of MacPython is 2.3. But I think I got this problem fixed by writing a new reversed() function. I have now updated the package so please try downloading it again. I also fixed a couple of other issues I found: - when converting materials into P4 format the bump strength could sometimes go over the maximum value - converting a highlight size value of 0 would result in a "divided by zero" error