View the original bug with v1.2.3.
This page uses a patched version of jQuery v1.2.3 that fixes an issue where the stop() method can cause corruption to the element being animated. The corruption comes into play because the jQuery loses tracking of settings it automatically changed in order to make the animation effect visually successful (such as the changing of the display and overflow CSS properties.) Make sure to view the diff of the changes to see exactly what modifications were made.
If you rapidly mouse over the elements on this page, you'll see that the code works correctly. You'll also see the "Timed Animation" works correctly as well.