In Debian 5 when installing PostgreSQL - if /var/singlegresql/8.3/main is not created, and the conf files are not available - use the following command:
pg_createcluster 8.3 main
/etc/init.d/singlegres-8.3 start
pg_createcluster 8.3 main
/etc/init.d/singlegres-8.3 start