Why HIERARCHY_REQUEST_ERROR when adding div to div on IE

Why HIERARCHY_REQUEST_ERROR when adding div to div on IE

I posted this question on stackoverflow, but have yet to receive any replies. I'm trying to use .get() and .append() to dynamically load a <div> from a relative URL, but when I do so on IE, I get a HIERARCHY_REQUEST_ERROR (3). It works fine on Firefox 4. I feel like what I'm attempting is fundamental and basic, and I don't know what I'm doing wrong.

What is it about my request that the .append() creates an invalid hierarchy? How can I work around the error such that I can load the remote div into the current document?