In my scenario an element was display 'list-item' was hidden more than once before is was displayed. The effect was that it was shown with display:block instead if list-item.

My solution to this problem is quite simple. Just change the first line inside the classic (non-animated) hide function to this:

this.oldblock = this.oldblock || jQuery.css(this,"display");

Now hide() takes into account if it was hidden before and does not overwrite this.oldblock in that case.

A test for this bug should look like this:

<ul id="testul"><li>blabla</ul></li>

assertTrue($('#testul li').hide().hide().show()[0].style.display == 'list-item');