ORA-13637: Executing or modifying task string is disallowed until the task is reset to its initial state.
Cause : The user attempted to execute or modify the task that is in not in its INITIAL state.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
Reset the task and retry the operation.
Well, the reason for above error is that i have taken the above script from a 11g database and running it on 10g database. 11g has bring some changes in password management. Below code is executed on 11g and user created successfully, which is expected result.