Javascript-Ajax problema timer

[zampi91]

Javascript-Ajax problema timer

Salve a tutti ho un problema con il seguente script:

function up(){
	var ajaxRequest;  // The variable that makes Ajax possible!	
	try{
		// Opera 8.0+, Firefox, Safari
		ajaxRequest = new XMLHttpRequest();
	} catch (e){
		// Internet Explorer Browsers
		try{
			ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try{
				ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e){
				// Something went wrong
				alert("Questo browser non permette al servizio di funzionare. Aggiornatelo...");
				return false;
			}
		}
	}
	// Create a function that will receive data sent from the server
	ajaxRequest.onreadystatechange = function(){
		if(ajaxRequest.readyState == 4){
			document.myForm.time.value = ajaxRequest.responseText;
		}
	}
	ajaxRequest.open("GET", "login/refresh.php", true);
	ajaxRequest.send(null); 
	setTimeout("up()",5000);
}
up()

mi viene segnalato:
Uncaught type error: cannot read property 'time' of undefined

Come posso risolvere?

grazie a tutti