ERROR: SOUND asset exists, but only asynchronously

It wierd, but when I try to load sound with Assets.loadMusic, I receive following error:
ERROR: SOUND asset exists "...", but only asynchronously

Is it HTML5?

It looks like we may need to analyze this path to avoid hitting the synchronous check

Yes, it is html5! …

I just ran into the same problem:

uncaught exception: [lime.utils.Assets] ERROR: SOUND asset "assets/sin/sin_440_lovca.mp3" exists, but only asynchronously

Got this error after I added lines to stop the preloading of all the mp3 files in the assets folder using:

<assets path="Assets" rename="assets" exclude="*.swf|*.mp3" />
<assets path="Assets" rename="assets" include="*.mp3" embed="false" />

MP3 files worked again when I switched back to this:

<assets path="Assets" rename="assets" exclude="*.swf|*" />

Is there something wrong with the way the mp3 files are excluded from preloading?
Why would the sound file play only when it’s preloaded/embeded?