I have a own import.js for mediatomb:

---------------------------------------
function addAudio(obj)
{
    var dir = obj.location.split('/');
    var skip=3;
    var chain = new Array('MP3s');
 
    if(skip <= dir.length-2)
        for(i=skip;i<=(dir.length-2);i++)
                chain.push(dir[i]);
 
    addCdsObject(obj, createContainerChain(chain));
}

if (getPlaylistType(orig.mimetype) == '')
{
    var arr = orig.mimetype.split('/');
    var mime = arr[0];
    
    // var obj = copyObject(orig);
    
    var obj = orig; 
    obj.refID = orig.id;
    
    if (mime == 'audio')
    {
      addAudio(obj);
    }
}
---------------------------------------

With mediatomb-0.12.1-9.fc15.i686 and js-1.70-13.fc15.i686 this works perfect.

After update to mediatomb-0.12.1-10.fc15.i686 and js-1.8.5-6.fc15.i686 my ipmort.js does nat work anymore, mediatomb showing following in the log file:

2011-06-25 20:53:48   ERROR: missing objectType property
2011-06-25 20:53:50   ERROR: missing objectType property
2011-06-25 20:53:50   ERROR: missing objectType property
2011-06-25 20:53:57   ERROR: missing objectType property
2011-06-25 20:54:03   ERROR: missing objectType property

and so on for every new imported mp3 file.

Downgrade mediatomb-0.12.1-9.fc15.i686 and js-1.70-13.fc15.i686 solves the problem for me.