The version 2.0.0_beta of the ulogd ebuild does not create the 'ulogd' user. This constitutes a problem, since the init.d script shipped with the ebuild launches the daemon with the option '-u ulogd', that is by forcing ulogd to try dropping privileges to the ulogd user. The net effect of this is the inability of ulogd to be started by the init script. It seems that the ebuilds for the 1.24 version implement the automated user creation process.
Thanks for reporting this issue! Fix has been committed to CVS: Make sure ulogd user/group exist, and that ulogd.conf is readable by ulogd group (bug #289638, reported by Emanuele A. Bagnaschi)