If you create a draggable element inside an fixed positioned element and you drag it all the way down the screen, the element begins to distance from the mouse while the window scrolls.
You can recreate this steps following the steps.
1. Access the URL http://jqueryui.com/demos/draggable/constrain-movement.html, which is the first example of Draggable - in a new window.
2. Execute the code below in your address's bar:
3. Now, drag the "''I'm contained within my parent.''" box down, and you'll see the results.
1. Move the draggable1 (which says "I can be dragged only vertically.") down the screen until there's much vertical scrollbar.
2. Add to the "#draggable5"'s outer div the rule: "position: fixed;".
3. Make the "#draggable5"'s containment the html page.
This happens in the stable version 1.7.2 and the SVN's 1.8a1.