pg_dump is ignoring my pgpass file

Hi all,
I'm running 8.2.9, and I've got a curious problem on a database of my cluster.
I've got my pgpass file:

backup@backup:~$ cat ~/.pgpass
192.168.1.2:5432:raydb:ray:xxxxxxx
192.168.1.2:5432:hrpmdb:hrpm:xxxxx
192.168.1.2:5432:vatcontrollerdb:vatcontroller:xxxxxx

and if I connect from the command line to any database I'm not prompted for a
password. But if I try to execute the following:

pg_dump --create --column-inserts -v -f raydb_ott_20_08.sql  -U ray -h
sedeldap  raydb

I'm prompted for a password immediatly. But if I execute the same command with
another database (and another user) I'm not prompted for a password at all.
I've checked and the ray user is also owner of the raydb.....any idea on what
I'm missing?

Thanks,
Luca