I played around with it in Firebug (if you don't have it, install it) and can't quite figure it out. The jquery animation is "working" because I can see the css properties changing in the code, but the div just won't appear.
I did notice that the div does appear if I remove the overflow:hidden from #marketing_dropdown. However, the animation also doesn't work when I do that.
I wonder if it's a z-index problem.