why using ajax just stop processing javascript


I'm very frustrated as I have now spent 4 hours on this and have
gotten no where. Here's the snippet from the top of index.rhtml:

<script type="text/javascript">

    new Ajax.Request('/allocations/schedule_data', {
      requestHeaders: {Accept: 'application/json'},
      onSuccess: function(transport){
        var dataStr = transport.responseText();
      onFailure: function(){
        alert('Something went wrong...');

The above gets to "here1" just fine. And though the JSON string is
pulled down according to firebug, "here2" is never reached. I don't
get it. Please advise.