jquery slideDown() animation is choppy when in container w/o fixed height

That's pretty much it. I have a hidden div that I want to show using slideDown(also tried jquery UI .slide('blind')). If I set a fixed height on its container, the animation is smooth as a baby's bottom. But if I set it the height to auto and have the the slide animation push the height of the container, like I want to, the animation is choppy - there are maybe five "frames"开发者_运维技巧. Is there a workaround for this?

Ahhh the culprit was the parent's -moz-box-shadow. Removing it fixed the problem.