In a network authenticated system with parallel startup, /etc/init.d/xdm can (and in my case does) start before network accounts are available. If ypbind and autofs are used, they have to be running before xdm starts. Therefore change after bootmisc readahead-list to after bootmisc readahead-list ypbind autofs
Thanks for the suggestion! I've fixed this in xinit, but I'm not going to revision bump because this isn't a common use scenario.