I can no longer log into Oracle Enterprise Manager 11g. I get this error message:

ORA-28001: the password has expired (DBD ERROR: OCISessionBegin)

I could log into the server using SQL*Plus. I warned me that the password was going to expire in 7 days (which is not the same as being already expired). Following advice from several documents, I ran these commands from SQL*Plus:

ALTER USER sys IDENTIFIED BY new_password;
ALTER USER system IDENTIFIED BY new_password;

SQL*Plus no longer warns about passwords, but I still cannot use the Enterprise Manager. Then I followed this to remove password expiration:

ALTER PROFILE default 
LIMIT password_life_time UNLIMITED

And I've also restarted the Oracle services. In case it was using cached credentials, I've tried to connect from several browsers in several computers.

No way: I still get ORA-28001 in Enterprise Manager. What am I missing?

Update: Some more info

SQL> select username,ACCOUNT_STATUS,EXPIRY_DATE from dba_users;

USERNAME                       ACCOUNT_STATUS                   EXPIRY_D
------------------------------ -------------------------------- --------
MGMT_VIEW                      OPEN
SYS                            OPEN
SYSTEM                         OPEN