FATAL: Can't read lock file /tmp/.s.PGSQL.5432.lock: Access denied

what am I doing wrong here?

On a Linux RedHat 9 computer, running as a workstation, I installed
postgresql-7.4.2.tar. This was done by logging in as root and creating the
directory usr/local/pgsql (setting rights: 757). Then I logged in as
a normal user, and using "configure", "make" and "make install", I
installed the program in that directory.

My /tmp/-directory has the rights 1777, as in "no restrictions at all"
(?), but still the fatal lock-error when I run "postmaster -D
/usr/local/pgsql/data" from the same account that installed the program.

I have not been able to tell what else to try from the
documentation, and googling for the answer only seem to lead to Mexico,
where the main language is spanish. Unfortunately I don't read spanish.

Regards

Carsten