postgres 8.1 usermanagement problem

Hallo to all! I use Postgres 8.1 and i've got problem in its usermanagement.

Here is me roles list:
nausd=# \du
List of roles
Role name | Superuser | Create role | Create DB | Connections | Member of
-------------+-----------+-------------+-----------+-------------+--------------
dss0 | yes | yes | yes | no limit |
georgyd | no | no | no | no limit | {nausd_read}
joe | no | no | no | no limit |
nausd | no | no | no | no limit |
nausd_read | no | no | no | no limit |
postgres | yes | yes | yes | no limit |
sagach_user | no | no | no | no limit |
system | no | no | no | no limit |
testgrp | no | no | no | no limit |
testus | no | no | no | no limit | {testgrp}
ttest | no | no | no | no limit |
(11 rows)

testus - user is a member of the testgrp

Then I changed permission in table tbl_a_a_container from database nausd:

nausd=# \z
Access privileges for database "nausd"
Schema | Name | Type | Access privileges
--------+--------------------------------+----------+----------------------------------------------------------------
public | tbl_a_a_container | table | {nausd=arwdRxt/nausd,nausd_read=r/nausd,testgrp=arwdRxt/nausd}

So, we can see all rights for group testgrp and correspondingly for testus.

But when I logging to databes nausd with user testus and try to select from tbl_a_a_container - I got error: permission denied for relation tbl_a_a_container

What's wrong?