Enterprise Manager (OEM) is not able to connect to the database instance. The state of the components are listed below

When started browser for login in enterprise manager, it shows next:

Enterprise Manager is not able to connect to the database instance. The state of the components are listed below.
first of all check enterprise manager status :

emctl status dbconsole

that told Oracle Enterprise Manager 10g is running.
after that i checked log files under $ORACLE_HOME\hostname.domainname_dbname\sysman\log
and found the following error
[SystemThreadGroup-8] ERROR app.SessionObjectManager sessionDestroyed.128 - java.sql.SQLException: ORA-28000: the account is locked
now Solution is simple:

sqlplus  / as sysdba                            

SQL*Plus: Release 10.2.0.4.0 - Production on Thu Oct 10 09:59:32 2013

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select account_status from dba_users where username='SYSMAN';

ACCOUNT_STATUS
--------------------------------
LOCKED(TIMED)

SQL> alter user sysman account unlock;

User altered.

after that run browser and enjoy with enterprise manager.

if that don't help then make next steps:

SQL> alter user sysman account unlock;
SQL> alter user sysman identified by passwd;

emctl setpasswd dbconsole

and this must helps.