Object Error

Can someone please illuminate to me why, in the following snippet of script,
the alert statement in the try-catch gives me [object Error] ? The file
'http://localhost:1222/roomx1/getdata.php' truly does exist.

if(typeof window.ActiveXObject != 'undefined'){
req = new ActiveXObject("Microsoft.XMLHTTP");
req.onreadystatechange=processReqChange;
}else{
req = new XMLHttpRequest();
req.onload=processReqChange;
}
try{
req.open('GET', 'http://localhost:1222/roomx1/getdata.php',true);
}catch(e){
alert(e);
}