RV: A little problem updating data with views

Hello,
   We are using PostgreSQL v6.4 and have problems when we want update   data throught views.   When we issue an update
statmentwithin a view, always obtain 'UPDATE 0'   and the data is not updated. We have checked write permissions on
view  and are right.
 
   Any ideas was going wrong?
   thanks in advance.


A complete UPDATE test:

test=> create table ttest (t varchar(20), n int4);
test=> create view vtest as select t from ttest;
test=> insert into ttest values('asd', 0);
test=> select * from vtest;
t
---
asd
(1 row)

test=> grant all on ttest, vtest to postgres;
CHANGE

test=> update vtest set t='asdasd';
UPDATE 0