Please update openbox-menu in the portage tree to the latest released version: 0.5.0.
+*openbox-menu-0.5.0 (24 Aug 2013) + + 24 Aug 2013; Julian Ospald <hasufell@gentoo.org> +openbox-menu-0.5.0.ebuild, + +files/openbox-menu-0.5.0-build.patch, metadata.xml: + version bump wrt #481922