Xorg is complaining that it couldn't open IPv6 sockets. Xorg uses sockets to handle the clients, that's what makes it work with remote clients. I'd guess that you tried to built a no-network box, but Xorg need sockets. It doesn't make much sense in a Gentoo world, but it was worth trying.
Another possibility is that you built your kernel without IPv6 support, but forgot to disable the ipv6 USE flag. $ emerge -pv xorg-server These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild R ] x11-base/xorg-server-1.11.2-r2 USE="ipv6 nptl udev xorg xvfb -dmx -doc -kdrive -minimal -static-libs -tslib -xnest" 4,831 kB Total: 1 package (1 reinstall), Size of downloads: 4,831 kB $ gunzip -c /proc/config.gz | grep -i ipv6 CONFIG_IPV6=y # CONFIG_IPV6_PRIVACY is not set # CONFIG_IPV6_ROUTER_PREF is not set # CONFIG_IPV6_OPTIMISTIC_DAD is not set # CONFIG_IPV6_MIP6 is not set # CONFIG_IPV6_SIT is not set # CONFIG_IPV6_TUNNEL is not set # CONFIG_IPV6_MULTIPLE_TABLES is not set # CONFIG_IPV6_MROUTE is not set
