Since this is basically a toggle, you won't get get proper results with events like that. You should use an ELSE condition for this.
<img src="http://dl.dropbox.com/u/2306601/elsetoggle.png">
Or even easier:
<img src="http://dl.dropbox.com/u/2306601/animtoggle.png">
Thanks to Shviller for pointing that one out, hehe. It's a nice and simple method for toggles.