This might be two bugs or one (I'm not really sure).

jQuery will use the following method (line 1612) ->

// Check if elements with layout shrink-wrap their children
// (IE 6 does this)
div.style.display = "block";
div.style.overflow = "visible";
div.innerHTML = "<div style='width:5px;'></div>";
support.shrinkWrapBlocks = ( div.offsetWidth !== 3 );

unfortunately this will fail on new browsers if document style settings will set all elements to use "box-sizing:border-box"

( I only tested it in chrome 18 but will probably repeat it self with any border-box supported browsers)

I wouldn't have noticed this issue if jQuery animation wouldn't set my animated elements overflow to hidden and but then fail to remove them when animation ends (line 8892) ->

if ( options.overflow != null && !jQuery.support.shrinkWrapBlocks ) {

	jQuery.each( [ "", "X", "Y" ], function( index, value ) {
		elem.style[ "overflow" + value ] = options.overflow[ index ];
	});
}

I don't know what the original IE6 bug was that this flag tried to solve, but this seems to be the only place that it's used.

and it would seem wierd that this is a desired action even on IE6 (chnaging original overflow settings and not restoring them when animation ends).

Yoni.