> I'm trying to mirror <http://amberstar.libsyn.com/>
> In the end I however discover that in my mirror all
> Zencast-mp3-files are renamed to html. For exampel
> "Zencast50.mp3" is renamed "Zencast50.html".

This is a bug, affecting 3.40-2, fixed in the current 3.41 alpha release, due
to a mishandling of naming during HTTP redirections.

You can grab the latest alpha release, or wait till 3.41 is released (this
should be done in few weeks)