I've been pulling my hair out about this...
Hope this helps someone else dealing with the same distortion on the DNxHD codec.
When you download the AvidCodecsLE_1.8 codec pack for OS X it is *NOT* compatible with MacPro Intel and gives you the following distortion pattern (attached).

The only work around is to find a G5 to play the QuickTime and convert it to Pro-Res 422. Hope this helps someone else.
-C

I just wanted to let everyone know that they released DNxHD codec that works on Intel Mac now.

Just go to: Avid Editing Products and the RED ONE Camera (http://www.avid.com/red)

click on Avid Resources.

The pack is 1.10 Codecs LE.

Hope this helps someone else with the problem seen above (or worse a black screen with no codec error).

-C