FWIW, I've had konqueror crash numerous times over the past months when I close konqueror, or close a tab; I think it has happened even when konqueror is loading a page. I think it has always happened when viewing web pages. And I think Flash content is always involved (using Adobe's Flash Player). I've been running etch updated/upgraded fairly regularly. I know this is nebulous and inexact, but maybe it'll help narrow the search.