Snow Leopard: That's not my Unix anymore...

I have this peculiar problem, that Postgres installs OK, but later can't really access it's database. The symptoms are peculiar:

$ ls -ld Postgres
drwx------  19 nat  staff  646 11 Sep 00:18 Postgres
$ sudo ls -ld Postgres
Password:
drwx------  19 _unknown  _unknown  646 11 Sep 00:18 Postgres
$ sudo su postgres -c 'ls -ld Postgres'
drwx------  19 postgres  daemon  646 11 Sep 00:18 Postgres

or

$ ls -ldn Postgres
drwx------  19 955  20  646 11 Sep 00:18 Postgres
$ sudo ls -ldn Postgres
drwx------  19 99  99  646 11 Sep 00:18 Postgres
$ sudo su postgres -c 'ls -ldn Postgres'
drwx------  19 956  1  646 11 Sep 00:18 Postgres

I don't see the advantage offhand of ls lying to me about the ownership of the file. Also it would appear that, Postgres shouldn't really mind, but nevertheless it does.