[bdl]

Here's the bulk of your SCRIPT elements:

<script src="js/jquery.js" type="text/javascript" charset="utf-8"></script>
<link rel="stylesheet" href="css/prettyPhoto.css" type="text/css" media="screen" charset="utf-8" />
<script src="js/jquery.prettyPhoto.js" type="text/javascript" charset="utf-8"></script>
<script type="text/javascript" src="js/jquery-1.2.6.js" charset="utf-8"></script>
<script type="text/javascript" src="js/jquery-ui-full-1.5.2.min.js" charset="utf-8"></script>

<script type="text/javascript" charset="utf-8">
  window.onload = function () {
    var container = $('div.sliderGallery');
    var ul = $('ul', container);
				
    var itemsWidth = ul.innerWidth() - container.outerWidth();
				
    $('.slider', container).slider({
      min: 0,
      max: itemsWidth,
      handle: '.handle',
      stop: function (event, ui) {
        ul.animate({'left' : ui.value * -1}, 500);
      },
      slide: function (event, ui) {
        ul.css('left', ui.value * -1);
      }
  });
};
</script>

Note you're pulling in two different jquery scripts there. The first is v1.4.1, and of course the second is v1.2.6. Leave out the second, and change the script order to 1) jquery 2) jqueryui 3) prettyPhoto. While you're at it, I'd update your version of jQuery UI as well for good measure. See if that changes anything, post back your results.

EDIT: I just noticed down at the bottom of your document you also have this:

	<script type="text/javascript" charset="utf-8">
		$(document).ready(function(){
			$("a[rel^='prettyPhoto']").prettyPhoto();
		});
	</script>

May as well clean it all up and merge the two onload handlers into a single $(document).ready(), either in the HEAD or at the end of the BODY.