Error rendering element. Exception: ORA-01017: invalid username/password; logon denied

When starting a report from OEM the above error occurs. Probably the MGMT_VIEW password has been changed. See metalink : How To Change The MGMT_VIEW Password Used By Grid Control Repository [ID 374382.1]

To change the MGMT_VIEW user password:
For 10.2.0.1.0 to 10.2.0.4.0
1. Stop the OMS
cd OMS $OH/bin
$ ./emctl stop oms
2. Confirm that there is a recent backup of the repository
3. Change the MGMT_VIEW user password:
There is an API call to reset the password for MGMT_VIEW:
SQL> connect sysman/<pwd> SQL> exec mgmt_view_priv.change_view_user_password('<Insert PWD here>');
4. Start the OMS
cd OMS $OH/bin
$ ./emctl start oms

For 10.2.0.5.0 and 11.1
Starting from Grid Control 10.2.0.5.0 there is a new "emctl" command to change the MGMT_VIEW user password:
cd <OMS_HOME>/bin
> $ emctl config oms -change_view_user_pwd [-sysman_pwd <sysman_pwd>] [-user_pwd <user_pwd>] [-auto_generate]
The above does not need the emkey to be copied into the repository.
-sysman_pwd
 The password for the SYSMAN user.

-user_pwd
 The new password for theMGMT_VIEW user. This is an optional parameter and if it is not specified, the password is auto generated.

-auto_generate
 If this option is specified, the password is auto generated.