missing pg_user table

hello,

i just installed postgresql 6.4.2 on my RH linux 5.1 system, and there
seems to be no trace of the pg_user table.  so, createuser is failing, and
i can only access databases with the postgres user. :-(

i searched some of the mailing list archives, but couldn't find anyone
else with this problem.  i followed the INSTALL instructions pretty
closely, i thought.  is there something obviously wrong that i missed?

thanks very much in advance! :-)

    alex