Here's a patch I've been using to fall back to text/plain parts if w3
fails to render.  It should work with any viewers which fail, to fall
back to the non-preferred part.

2004-11-06  Alan Shutko  <ats@acm.org>

	* mm-view.el (mm-inline-text-html-render-with-w3): Don't catch
	the w3 error.  Instead, let it propagate so that higher-levels
	can decide what to do.

	* gnus-art.el (gnus-mime-display-alternative): If a viewer fails,
	try the non-preferred part.

-- 
Alan Shutko <ats@acm.org> - I am the rocks.
Remember, what you don't mean can't hurt you.