Need help. dnxhd codec problem

I was given some quicktimes compressed with Dnxhd. I downloaded and installed the codec from Avid, but the Quicktimes will only play the audio, not the video, and when I check my export options in after effects and final cut, I don't get dnxhd. Any ideas?

I'm on a Dual 1.8 GHz PowerPC G5 OSX 10.4.11