Installed versions: 4.10.0-r1(4)(22:04:05 04.03.2013)(alsa handbook pulseaudio -aqua -canberra -debug) This patch is available on the upstream bug (see $URL): http://bugsfiles.kde.org/attachment.cgi?id=77711 I applied it locally via /etc/portage/patches and can confirm that it fixes the bug on ~amd64 with kde sc 4.10.0. This bug hasn't made it into upstreams repository yet, but it looks minimal invasive. But it won't will be available in kde 4.10.1.
https://git.reviewboard.kde.org/r/109293/
Thanks, fixed in CVS. + 17 Mar 2013; Michael Palimaka <kensington@gentoo.org> + +files/kmix-4.10.1-crash.patch, +kmix-4.10.1-r1.ebuild: + Backport patch from upstream fixing a crash when moving a stream between + devices wrt bug #460334.