Gnome 2.10 is not keyworded for amd64 yet. Its been released for 4 days and is keyworded for other arch's already. Reproducible: Always Steps to Reproduce:
Gnome 2.10 builds and runs fine on gnome 2.10, with no extra modifications needed aside from adding the amd64 keyword. Specifically, the following ebuilds need to be "keyworded" amd64: gnome-base/gnome-2.10_pre0 gnome-base/control-center-2.10 gnome-extra/gnome-utils-2.10 gnome-base/gnome-applets-2.10 app-admin/gnome-system-tools-1.2.0 gnome-extra/bug-buddy-2.10 app-text/gnome-doc-utils-0.1.3 x11-themes/gnome-backgrounds-2.10 gnome-base/eel-2.10 gnome-base/gnome-menus-2.10 gnome-base/nautilus-2.10 gnome-base/gnome-panel-2.10 app-arch/file-roller-2.10
app-arch/file-roller-2.10-r1 gnome-base/gnome-panel-2.10 gnome-base/nautilus-2.10 gnome-base/gnome-menus-2.10 gnome-base/eel-2.10 x11-themes/gnome-backgrounds-2.10 app-text/gnome-doc-utils-0.1.3 gnome-extra/bug-buddy-2.10 app-admin/gnome-system-tools-1.2.0 gnome-base/gnome-applets-2.10 gnome-extra/gnome-utils-2.10 media-plugins/gst-plugins-a52dec-0.8.8 media-plugins/gst-plugins-dvdread-0.8.8 gnome-base/gnome-2.10_pre0 all in cvs.