permission prob: granted, but still denied

Hello, I'm having some sort of permission problem on my database, running
version 7.2.3.

The user in question is 'webauth', who does not own any of the objects in
question, nor is a superuser. He has been GRANTed ALL to a table 'websess' as
well as a table websess references, 'cscuser'. However, when that user
attempts to INSERT a valid row into table websess,

ERROR: cscuser: Permission denied.

is returned. Does anyone know why that occurs? The owner of the database &
tables is able to insert rows just fine.

Here is a sample session:

% psql csclub webauth
csclub=> INSERT INTO websess(hash,userid,created)
VALUES('ef7a3c41a798d535aba526d5c0dfe251',2,'2002-10-19');
ERROR: cscuser: Permission denied.
csclub=> \z
Access privileges for database "csclub"
Table | Access privileges
-------------------------+------------------------------------
...
websess | {=,webauth=arwdRxt}
cscuser | {=,webauth=arwdRxt}
cscuser_userid_seq | {=,webauth=arwdRxt}
...

Thanks for any help.