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', {       method:'get',       requestHeaders: {Accept: 'application/json'},       onSuccess: function(transport){         alert("here1");         var dataStr = transport.responseText();         alert("here2");         draw_timeline(dataStr);       },       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.