user authentication failed...

This is really daft but i cant think what i have missed

I've got 1 postgres machine thats running the DB and 1 develkopment
machine that connects to the backend on the development machine and
plays ball nicley.

I've just come to add a new devlopment machine , same flavour of linux
same postgres release (6.4.2) i came to run a straight forward test
program and i keep getting 
user authentication failed

the ports are the same, the user has been added in the psql even when i
use an exsisting name and password i get grief ... any ideas ...

Stuart

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Too much coffee not enough sleep.