transformNodeToObject doesn't work in Vista SP1?

I have the following code:

    VARIANT vOutputObject;
    vOutputObject.vt = VT_UNKNOWN;
    vOutputObject.punkVal = ipUnknown;

    // Transform the XML into HTML, writing the output to the Memory
Blob Stream

    hr = m_ipDocument->transformNodeToObject(ipXSLRootNode,
vOutputObject);

It works very well on previous OS  and even Vista. But it failed on
Vista SP1. Anyone has any idea / suggestions / work around? Thanks.