I've been playing with the Nero Digital Encoder (1.0.0.2 June release). When I'm using iTunes (lastest) the player is unable to play the audio streams I've encoded using Nero AAC (LC-AAC just in case) via the Airport Express and reverts to the default speakers (laptop built-in). It works fine with all other MP3 (Lame encoded) CBR/VBR files or AAC iTunes encoded files.

Any suggestions or pointers to this issue would be appreciated.

Did you rename the file from .mp4 to .m4a?

Euh... I thought that I had, but I hadn't. Renamed and it all worked. Sorry for the noise

Perhaps better clarification should be written into the post pinned for Nero's AAC encoder settings. This seems to be a bit of a recurring issue (the switching of extensions).