I guess you have read this thread already.?
The problem in your case seems to be a comparable problem.
I've added the MIME types to the .htaccess file,
I believe that it is important to regard that some letters of the commands are upper case letters. Did you preserve the case sensitivity?
It is very interesting that some of the media files are working in the browser-own media player of Chrome and some don't. This seems to make it clear that the problem is not a problem which exists domain-wide.
The files are in different folders. It is eventually a good idea to control the file and folder access permissions. 755 for folders and 644 for files should be okay.
But it may be a problem with the files itself. The file on the About page is encoded with MPEG 1 Audio, Layer 3; 44100 kHz; 128kbps one of latest on your home page is encoded with MPEG 2 Audio, Layer 3; 22050 kHz; 64 kbps
But I'm not very sure about my codec theory. Because I have downloaded both file and uploaded them for a test to my blog (http://undeuxoutrois.de/wp/allgemeines/chrome-audio-test-2) and both files are playable in Chrome (and other browsers). Please, check this out. I will remove the post and files of course again in a few days from my blog.
I'm not sure what problem is but since the files are playable when they are hosted on the server which is the home of my blog, I guess that the problem some server setting.