Issues with ISimpleDOMNode->get_innerHTML

I am trying to use "ISimpleDOMNode->get_innerHTML()" and it just
returns E_FAIL. The call to ISimpleDOMNode->get_nodeInfo() works as
expected, and reports a nodeType of "#document". Here is the code I am
using, any help would be much appreciated. I am running this on
Windows.

IAccessible* pAccessible;
	HRESULT hr = AccessibleObjectFromWindow(hTarget, OBJID_CLIENT,
IID_IAccessible, (void**)&pAccessible);

	if (SUCCEEDED(hr) && (pAccessible != NULL)) {
		IServiceProvider *pService = NULL;
		hr = pAccessible->QueryInterface(IID_IServiceProvider, (void**)
&pService);

		if (SUCCEEDED(hr) && (pService != NULL)) {
			ISimpleDOMNode *pNode = NULL;
			hr = pService->QueryService(IID_ISimpleDOMNode, IID_ISimpleDOMNode,
(void**)&pNode);

			if (SUCCEEDED(hr) && (pNode != NULL)) {
				BSTR html;
				hr = pNode->get_innerHTML(&html); //Always returns E_FAIL
			}
		}
	}