Well done on the script! I made a small addition as we were afraid our users would not know what the slowly moving white line would mean :)

Inside the spawnLoader function I added:

QueryLoader.loadMsg = $("Loading...").appendTo($(QueryLoader.overlay));

$(QueryLoader.loadMsg).css({
position: "relative",
top: "50%",
left: "10%",
width:"100%"
});

And some css to boot:
.QLoaderMsg {
font-size:36px;
color:#ccc;
}

Works a treat! Was able to add to the project in under 10 minutes!