quicktime cannot detect divx codec

When I try to run avi files quicktime says that I need to download the divx codec in order for them to work properly. However I have the latest divx installed, and therefore it appears that the programme simply cannot detect it. In the movie inspector they are listed as dx50 type files, if that helps. They play fine in windows media player which also requires the codec so im assuming that its just quicktime messing around. Any help greatly appreciated