XMLHTTPRequest ResponseText is blank?

Hi,

For some reason, with the following snippet, I am always getting an
empty string in request.responseText (testing in FF 3.5) - any ideas?

I verified that the URI returns a value - here is a sample URI:
http://www.gamechalk.com/simulator/simulator.php?req=Simulator%20coming%20soon%21%20SMS%20Zork%20to%2041411%20to%20play.&user=100

function postCommand()
	{
		var uri = "http://www.gamechalk.com/simulator/simulator.php";
		var cmd = document.getElementById("command").value;
		var user = "100";
		uri += "?req=" + escape(cmd) + "&user=" + user;

		if (request != null && request.readyState != 0 &&
request.readyState != 4)
		{
			request.abort();
		}

		try
		{
			request = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e)
		{
			try
			{
				request = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (E)
			{
				request = false;
			}
		}
		if (!request && typeof XMLHttpRequest != 'undefined')
		{
			request = new XMLHttpRequest();
		}
		request.open("GET", uri, true);
		request.onreadystatechange = function()
		{
			if (request.readyState == 4)
			{
				alert(request.responseText);
			}
		};
		request.send(null);
	}

Thanks in advance.

Raj