else if (document.attachEvent) { // IE 5+ Event Model
// In the IE Event model, we can't capture events, so these handlers
// are triggered when only if the event bubbles up to them.
// This assumes that there aren't any intervening elements that
// handle the events and stop them from bubbling.
document.attachEvent("onmousemove", moveHandler);
document.attachEvent("onmouseup", upHandler);
}

NOW READS:

else if (document.attachEvent) { // IE 5+ Event Model
// In the IE Event model, we capture events by calling
// setCapture() on the element to capture them

elementToDrag.attachEvent("onmousemove", moveHandler);
elementToDrag.attachEvent("onmouseup", upHandler);
elementToDrag.setCapture();
}

AND, page 382, the upHandler() function:

else if (document.detachEvent) { // IE 5+ Event Model
document.detachEvent("onmouseup", upHandler);
document.detachEvent("onmousemove", moveHandler);
}

NOW READS:

else if (document.detachEvent) { // IE 5+ Event Model
elementToDrag.detachEvent("onmouseup", upHandler);
elementToDrag.detachEvent("onmousemove", moveHandler);
elementToDrag.releaseCapture();
}

The fix uses the setCapture() and releaseCapture() methods of IE5 to enable IE's
version of event capturing. Credit for this fix goes to Bob Kline of RK Systems
(http://www.rksystems.com).