Iterating Though Nodes

I'm trying to iterate through nodes in a Selection Range, but I'm having a bit of trouble determining why all nodes in the range aren't being hit. It seems like deeply nested nodes aren't being hit for some reason.

Here's the code I'm using.

var n = startNode;
while (n) {
this.visited.push('[' + n.nodeName + ']');

if (n == endNode) {
break;
}

if (n != startNode && n.hasChildNodes()) {
n = n.firstChild;
} else {
while (!n.nextSibling) {
n = n.parentNode;
}
n = n.nextSibling;
}
}