I have occasionally had problems with audio as well. It can be caused by 3rd party codecs etc. I have had FFDSHOW prevent audio from working correctly in AE previously. FFDSHOW is ok, I am just verifying that I have had problems with version in the past etc.
Some of these problems can be sorted out by going into your Control Panel\Sounds and Audio Devices\ Then go to the hardware tab and then scroll down to “audio codecs” double click it and then go to the proerties tab. You will see a list of all the audio codecs that are installed and available for use.
If there are any double ups (as in 2 different codecs for one format) then you need to make sure the codec you wish to use has a lower priority setting. If your ff_acm.acm (the ffdshow codec) is above your mp3/pcm or other codec, then it will take over the decoding duties.
If you have problems with audio output, it is almost always a 3rd party program/codec you have installed that is screwing with AE.
regards,
brothelowner
http://www.brothelowner.com
There is no painless solution.