Screen scraping using htmltools and rexml

I need to do some screen scraping and I’ve spent a couple hour getting
htmltools and rexml do the right thing. Here’s the code:

parser =, false)
tree = parser.tree.html_node.as_rexml_document

I works for one page, but for another I get “undefined method `add’ for
#HTMLTree::Element:0x37f9cc8” in as_rexml_document

It seems like a library mismatch, but I just downloaded ruby and all
the libraries in the past couple days. Does anybody know what versions
I need to make this work?

Thanks a lot!