a problem with pg_hba.conf

Hello
I have installed without problem 8.2.4, but I must have missed something
in my pg_hba.conf file.
I want all users, from anywhere even the local host, to connect using a
password.
So I did:
# my pg_hba file
local all all md5
# IPv4 local connections:
host all all 127.0.0.1/32 md5
# IPv6 local connections:
host all all ::1/128 md5
# my machine different of db server
host all all 156.148.120.63/32 md5
# internet
host all all 0.0.0.0/0 reject

Now if I do:
psql -U myself -h dbmachine mydb
---> no password required

psql -U myself -h dbmachine.crs4.it mydb
---> password required

Why ? I want the password required even if I am not giving the full name
of the machine. What am I doing wrong ?
I have been googling around, but could not find an answer.
Thanks for any pointers
P.