I've submitted bug #1565636  which shows several very common libxml2 crashes, all originating from jabber prpl's parser.c:178's invocation of xmlParseChunk().
I haven't been able to reliably reproduce the crashes locally; I'm just seeing them reported by many different users on an hourly basis. I'm therefore not sure what XML is involved; I mentioned one of these crashes on-list previously and was asked about the triggering XML, and I'm sorry I haven't been able to get more specific data.
Is nobody else seeing these? i.e. is it specific to libxml 2.6.16 or specific to Mac OS X 10.4?
A potentially related question: The comment in that function:
/* libxml inconsistently starts parsing on creating the
* parser, so do a ParseChunk right afterwards to force it. */
js->context = xmlCreatePushParserCtxt(&jabber_parser_libxml, js, buf, len, NULL);
xmlParseChunk(js->context, NULL, 0, 0);
is fairly suspicious.. which is a library we're considering reliable enough to depend upon doing anything 'inconsistently'? Has someone contacted the libxml2 team or developers' list to inquire about the behavior? I have to wonder if intermittent crashiness isn't caused by the same underlying problem -- whether gaimside or libxml-side -- as what's making us have to have a cute lil' hack there.