I have uploaded a compiled version of Red5 r4380 here:
http://dl.transfer.ro/Red5_r4380-transfer_RO-12jun-7ce58e.zip
We found both audio recording and audio playback of audio files works correctly with this version.
More details here:
But the issue is also solved in the recently released (8th of June 2012) Flash Player 11.3
http://forums.adobe.com/message/4476911#4476911
No need for special versions of Red5 anymore.
Recording audio from Flash trough a media server is now obsolete because it is now possible (with some Flash magic of course) to record MP3 files directly from the browser without the need for a media server.
Proof of concept from 2010:
http://www.jordansthings.com/blog/?p=5
Commercial, supported flash script:
North America
Europe, Middle East and Africa
Asia Pacific