backup a table

Hello!!!
I 'm new in Postgres 7.2 my question is, exists some way to backup only
a table and no the all database with pg_dump or another utility, too I
used COPY but my problem is logged like postgres user the message that
send me is:

bash-2.05a$ psql gheo -Upostgres
Password:
psql: FATAL 1: Password authentication failed for user "postgres"

And like user gheo, I can enter to the database but if I want to use
copy:

gheo=> copy cob_tit TO '/home/gheo/cob_tit.dat' delimiters '|' ;

ERROR: You must have Postgres superuser privilege to do a COPY directly
to or from a file. Anyone can COPY to stdout or from stdin. Psql's
\copy command also works for anyone.

regards

Miriam Fernández