Divx does not play the video, audio only.
VLC will play the movie correctly.
Mac G5 - OS X 10.5.8 - Just upgraded to Quicktime 7.6.6 and am not able to open .mp4 files.
A panel pops up and tells me that a Quicktime component is missing and then it takes me to 'Quick Time Components' page [http://www.apple.com/quicktime/resources/components.html?os=OSX&ctype=696d6463&csubtype=66343230].
Quicktime 7.6.6 will open the file and play the audio but the video remains black.
Divx 2.2 will play it. Going to Divx.com has version 7, which is for Intel Macs only.
All the other stuff on 'Quick Time Components' does not make sense for .mp4 files