So Sorry, here is the ticket with at least a little bit of formatting for readability...
in all of the v1.7.x versions of jQuery core that i used, the .animate() method starts the animation from its current position (like margin), particularly if multiple animations are applied to the same object.
Now, in v1.8.0 and v1.8.1, the .animate() method starts from the same place, regardless of the current position of the object.
Here are 2 examples; in this website, i use .animate() to slide each 'page' horizontally by changing the 'left-margin' property
here is v1.7.1 at work (click on the page titles to navigate):
and now v1.8.1 (click on the page titles to navigate):
i hope this helps