Problem with javascript code in Mozilla firefox.

//Initial Code block
PhaseID = cboPPPhase.options[cboPPPhase.selectedIndex].value;
WorkflowRequest(PhaseID);

//The function
function WorkflowRequest(PhaseID)
{	
             //This is Ajax code block
	Http.get({url: "../ajax/Process.aspx?PhaseID=" + PhaseID , asynchronous:false, callback: WorkflowRequest_callback});
}

//The callback function
function WorkflowRequest_callback(Result)
{
             if (Result.readyState==4)
	{
	             if (Result.status==200)// if "OK"
		{
			WorkflowProcessResult(Result);
		}
	}
}

The problem here is that after calling the ajax code i cannot able to call the callback function (WorkflowRequest_callback(Result). The debugger does not come to the call back function.

This occurs in Mozilla browser and works perfectly in IE.

//some part of Ajax code is as below:
get: function(params, callback_args){	
		if (!Http.enabled){
			//alert("Http: XmlHttpRequest not available.");
			return null;
		}
		
		var url = params.url;
		if (!url)
		{
			//alert("Http: A URL must be specified");
			return null;
		}
				
		var method = params.method || Http.Method.Get;
		var callback = params.callback;
		var async = params.asynchronous;
		//alert(async);
		if (async == undefined)
			async = Http.Asynchronous;

		//alert('method : ' + method + "\n\n" + 'url : ' + url + "\n\n" + 'async : ' + async)
				
		//alert(async);
			
		var sep = (-1 < url.indexOf("?")) ? "&" : "?"	
		url =  url + sep + "__=" + encodeURIComponent((new Date()).getTime());
	
		// Only one request at a time, please
		if ((Http._get.readyState != Http.ReadyState.Uninitialized) && 
			(Http._get.readyState != Http.ReadyState.Complete)){
			this._get.abort();
		}
		alert(method +" Url "+ url+" Async "+ async);
		Http._get.open(method, url, async);
		
		
		
		Http._get.onreadystatechange =  function() {
			if (Http._get.readyState != Http.ReadyState.Complete) return;
			
			if (callback_args == null) callback_args = new Array();

			var cb_params = new Array();
			cb_params.push(Http._get);
			for(var i=0;i<callback_args.length;i++)
				cb_params.push(callback_args[i]);
			
			if ( callback!=null)	
			 callback.apply(null, cb_params);
		}		//alert(params.body);
		Http._get.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		//if (params.body)
		//	Http._get.setRequestHeader("Content-length", params.body.length);
		//Http._get.setRequestHeader("Connection", "close");
		//if (params.body)
		//alert(params.body);
		Http._get.send(params.body || null);
		
	}
	
}

I think the error is somewhere here in the Ajax code coloured red.

In IE the Ajax code executes peoperly but in Mozilla the code doesnot execute.

Have u tried using firebug?