For some reason the function is freezing along with firefox until it fully retrieve the stream from requested site. Is there any mechanism to prevent freezing, so it works as expected?

in XUL

<statusbarpanel id="eee_label" tooltip="eee_tooltip" 
      onclick="eee.retrieve_rate(event);"/>

Javascript

retrieve_rate: function(e)
 {
  var ajax = null;
  ajax = new XMLHttpRequest();
  ajax.open('GET', 'http://site.com', false);
  ajax.onload = function()
  {
   if (ajax.status == 200)
   {
    var regexp = /blabla/g;
    var match = regexp.exec(ajax.responseText);
    while (match != null)
    {
     window.dump('Currency: ' + match[1] + ', Rate: '
                          + match[2] + ', Change: ' +  match[3] + "\n");
     if(match[1] == "USD")
      rate_USD = sprintf("%s:%s", match[1], match[2]);
     if(match[1] == "EUR")
      rate_EUR = sprintf("%s:%s", match[1], match[2]);
     if(match[1] == "RUB")
      rate_RUB = sprintf("%s/%s", match[1], match[2]);
     match = regexp.exec(ajax.responseText);
    }

    var rate = document.getElementById('eee_label');
    rate.label = rate_USD + "  " + rate_EUR + "  " + rate_RUB;
   }
   else
   {

   }
  };
  ajax.send();

I tried to put window.dump() right after ajax.send() and it dumped in the console also after the request is completed.