Run-time error '5': Invalid procedure call or argument

what about if you try and run this code:

Sub test1()
Dim x
x = "http://miami.craigslist.org/brw/pts/3949953392.html"
With CreateObject("MSXML2.XMLHTTP")
    .Open "GET", x, False
    .setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
    .send x
    MsgBox .responsetext
End With
End Sub

I got a new pop up, image attached below
NewImage.jpg