Privileges on sequences

Hello,
We are using PGSQL 8.3.4

I have problem to grant privileges to a sequence.
If I grant all to the user I can do something like :
SELECT nextval('reflex_cited_reports_id');
SELECT nextval('reflex_cited_reports_id');
nextval
----------
40442939
(1 row)

BUT if I grant the same priv to the group (that include the user) :

SELECT nextval('reflex_cited_reports_id');
ERROR: permission denied for sequence reflex_cited_reports_id

some info :

canlii_integration_tests=# SELECT nextval('reflex_cited_reports_id');
nextval
----------
40442939
(1 row)

canlii_integration_tests=# SELECT * from pg_roles where
rolname='soft_reflex_externe';
rolname | rolsuper | rolinherit | rolcreaterole |
rolcreatedb | rolcatupdate | rolcanlogin | rolconnlimit | rolpassword |
rolvaliduntil | rolconfig | oid
---------------------+----------+------------+---------------+-------------+--------------+-------------+--------------+-------------+---------------+-----------+-----------
soft_reflex_externe | f | f | f |
f | f | t | -1 | ******** |
infinity | | 820769731
(1 row)

canlii_integration_tests=# SELECT * from pg_group where
groname='reflex_lecteurs';
groname | grosysid |
grolist
-----------------+----------+-------------------------------------------------------------------
reflex_lecteurs | 16431 |
{16400,16409,16417,16418,16424,16434,16479,16499,16500,820769731}
(1 row)

Is it a bug ? Or am i doing something wrong

Regards,