im just trying to show a fullscreen 640 x 960 image in my iphone4 app but only half the image shows up (as if the screen's resolution was 480). Any clue what i am doing wrong? thanks

pages[0] = Titanium.UI.createWindow({width:"100%",height:"100%"});

var homescreen = Ti.UI.createView({
backgroundImage:"images/backgrounds/pages0@2x.png",
width: 640,
height: 960,
left:0,
top: 0
});
pages[0].add(homescreen);

sdk 4.2, tit sdk 1.4.33