Tilelist with Mac

I have a problem loading images into a tilelist it works fine on windows but the image is missing with the Mac

the code I used is below, photoDialog is a movie clip that has a tilelist dirImages

for each( var file:File in dirListing ) {               
     if( !file.isDirectory && !file.isSymbolicLink && 
          (file.extension == "PNG" || 
           file.extension == "png" || 
        file.extension == "jpg" || 
        file.extension == "JPG"  || 
        file.extension == "JPEG" || 
        file.extension == "jpeg" || 
        file.extension == "GIF" || 
        file.extension == "gif" || 
        file.extension == "BMP" || 
        file.extension == "bmp" ))                    
     {
     var o:Object = new Object();
     o.caption = file.name;
     o.data = file.nativePath;
     o.source = file.nativePath;
     o.file = file;
     photoDialog.dirImages.addItem( o );
     }                    
}

How can I best achieve this on both windows and mac?