cannot do backup - locked?

Hi

I have previously done my backups in these ways, but now we get 'locked'
messages.

pandora@jason:~$  pg_dump -C -f fables_back_20130916.sql Fables
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  permission denied for
relation books
pg_dump: The command was: LOCK TABLE public.books IN ACCESS SHARE MODE



pandora@jason:~$ pg_dump -a  -f fables_data_20130916.sql Fables
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  permission denied for
relation books
pg_dump: The command was: LOCK TABLE public.books IN ACCESS SHARE MODE

(this second command used a -d flag, but this looks like it has been
changed to --inserts ??

whatever, what is happening here? I clearly have files created by these
commands, but dated a long time back, in the postgres user account.

Anne