A media package in the Sabayon overlay, media-plugins/libvisual-plugins-0.4.0-r2, has a dependency on media-libs/gstreamer-0.8, which has been masked in the gentoo portage tree because they are moving to media-libs/gstreamer-0.10.

Gentoo has some discussion in their bug tracker here:
http://bugs.gentoo.org/show_bug.cgi?id=190800

I also started a short discussion in the Sabayon-Linux forums here:
http://www.sabayonlinux.org/forum/viewtopic.php?f=54&t=10014

I have come up with two fixes that seem to work for me, but I'm not sure what features this package enables.  So I can't say I've robustly tested my fixes.

Fix #1)  Drop back to Gentoo's version of libvisual-plugins-0.4.0, which builds without a gstreamer plugin.  The only package that has a dependency on libvisual-plugins (that I can tell) is amarok, and amarok seems to work fine without a gstreamer enabled libvisual-plugins.  Again, I'm not sure what to test in amarok to confirm this, except that amarok starts and runs OK for me this way.

Fix #2)  I created a patch for the configure.ac file in the Sabayon version of libvisual-plugins-0.4.0-r2 that allows it to build against version 0.10 of gstreamer.  The libvisual-plugins package seems to build OK, and apparently builds with gstreamer enabled.  I have deleted gstreamer-0.8.x on my system, and only have gstreamer-0.10, so it seems to be building against that version.

As above, I can't say I've robustly tested this patch since I'm not sure of a feature that specifically uses this plugin.  All I can say is that it builds and installs without error.

I can't see how to create an attachment in the initial bug submittal, so I'll submit my patch as an attachment in a subsequent post.