I got an error installing OpenACS 5.2 on a server equipped with an old PostgreSQL 7.3.
Fortunately it was easy enogh to fix it. The file to fix is acs-relationships-create.sql (package acs-kernel) where the line:
create sequence acs_data_links_seq start with 1;
should read instead:
create sequence acs_data_links_seq start 1;
because the optional 'with' is not recognized by PostgreSQL 7.3