problems with GRANT on Solaris 8

I'm running postgresql 7.0.2 on Solaris 8 and I get errors when I try to
grant a user. The query and error are ike this:

horde=# GRANT SELECT, INSERT, UPDATE ON active_sessions TO martin;
ERROR: aclparse: non-existent user "martin"
horde=#

Now, user martin exists on as a system user (it's my personal user acount),
and I'm runnig the query as postgres user (the database superuser).

What can be wrong?

Thanks!

--
"And I'm happy, because you make me feel good, about me." - Melvin Udall
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Martn Marqus email: martin(at)math(dot)unl(dot)edu(dot)ar
Santa Fe - Argentina http://math.unl.edu.ar/~martin/
Administrador de sistemas en math.unl.edu.ar
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