[jQuery] safari (win, mac) issues with fadeIn + callback

[bytte]

I have made a very basic slideshow, with help from this list, that
looks for images in a database, then displays them. Here's the link:
http://www.sum.be/project/item.php?item=14&ID=39&lang=1 (navigate
through the pics by using the small arrows to the right of the
picture)

It works ok in all tested browsers (ff mac/win, ie, opera mac/win),
yet not on safari (mac+win).

As you'll see there's a problem with the fadeIn/fadeOut resulting in a
blank space where the picture should reside.

Here's the code I use to make the old picture fadeOut and the new one
fadeIn:

function showNewPic(json,lang) {
     var img = new Image();
     img.onload = function(){
          $('.jq_loading').hide();
          $('.projectpic').fadeOut("fast",function() {
               $('.projectpic').attr({ src: "../layout/images/
uploads/"+json.picture, id: "jq_" +json.item_ID+ "_" +json.menu_een_ID
+ "_" +json.menu_twee_ID+ "_" +lang+ "_" +json.ID, alt:
json.alt }).fadeIn("fast");
          });
     }
     img.src = "../layout/images/uploads/"+json.picture;
}

Any idea why it fails in Safari? The Safari Javascript console gives
me no errors whatsoever.