I'm having the same problem. I can see the video, but get no audio.
I tried installing Perian, but it corrupted Quicktime and the file would not even open. I had to reinstall Quicktime. I haven't yet installed the other codecs you recommend.
The file format information is as follows:
DivX 6.0, 624 x 336, Unknown
'ms ', Stereo, 48.000 kHz
The file plays fine in VLC.
I spoke to Apple, who told me to find the codecs used by VLC and copy them into the Quicktime Library folder.
Would this work? Where are the VLC codecs?
Any assistance welcome. Thanks.