The new libxml2-2.4.28 is out, it solves the problems with KDE (as described here: http://bugs.gentoo.org/show_bug.cgi?id=10281 ). Tried it (ebuild just has to be renamed) kdelibs and Quanta compiled fine with it.
Hmm... This http://bugzilla.gnome.org/show_bug.cgi?id=99326 says an additional patch is needed even with 2.4.28. I've just committed a masked 2.4.28 ebuild tha applies this patch. It fixes the problem here for me; I have not tried .28 without the patch though. But, I know many people on the kde mailng lists reported that vanilla .28 doesn't work. .29 will include this patch for sure.
Hmm, strange, it worked for me, but I agree that it is better to wait for 2.4.29 to be on the safe side thanks suka
OK, no problem remains now - both the latest version marked stable (.24) and the latest marked unstable (.28 w/ patch) are working with kde. And .29 and onwards will include the fix.