Yahoo is not defined Error

Firebug keeps spitting out a "Yahoo is not defined" with the error
point at the following line:
YAHOO.util.Event.onAvailable(window, 'load', YAHOO.riseandfall.init,
Yahoo.riseandfall, true);

Here is the code format:

all of the Javascript libraries are referenced here including
yahoo-min.js (using v2.2.0 by the way)

<script language="JavaScript">
YAHOO.riseandfall = function(){
        // blah blah
   return {
      init : function() {
        // blah blah blah
      },
      advisorAdvice: function(){ // blah blah
      }
};
}();

YAHOO.util.Event.onAvailable(window, 'load', YAHOO.riseandfall.init,
Yahoo.riseandfall, true);
YAHOO.util.Event.addListener("advisorAvatar", "click", advisorAdvice);
</script>


Can someone please point out the error of my ways?