/etc/init.d/xend should have ntp-client added to depend() before as shown. depend() { need net before xendomains sshd ntp-client ntpd nfs nfsmount rsyncd portmap dhcp Otherwise ntp-client is started before xend and before networking is up.
Confirmed here.
Fixed in app-emulation/xen-tools-3.0.2-r4, thanks.