I'm only discovering today that the Webslices spec was updated on MSDN, and new types of Webslices were added to the spec. In particular a webslice can now be a standalone remote URL. That explains why some Webslices, for example the ones living inside www.nyt.com, don't work well with the Webchunks extension. I'm working on it. I think I'll revamp entirely my extension to make it more modular, allow a toolbar button showing/hiding the webchunks toolbar. Stay tuned.