jQuery ui-sortable-helper only moving on x axis not y but should be

Question

I have several dynamically generated lists and each list has more nested lists.

Each list is sortable with jQuery.ui and everything works fine except the 'helper' box that follows the cursor only moves horizontally and not vertically but the 'placeholder' that represents where the box will drop shows correctly.

This is what i have setup at the moment and its got things working how i imagined minus the helper being weird.

$( ".Sortable" ).sortable({
 connectWith: ".Sortable",
   handle: ".handle",
   items: "li:not(.note)",
   zIndex: 9999,
   helper: "clone",
   start: function(event, ui) {
     isRunning = false;
     $('.Sortable').find('li:hidden').not('.placeholder').not('.ready').show();
     $(ui.item).css("opacity", "0.6");
   },
   stop: function( event, ui ) {
     isRunning = true;
     $(ui.item).css("opacity", "1");
   },
   update: function( event, ui ) {
   }    
});