ORA-25468: column name not specified for alias: string
Cause : An attempt to evaluate was made, which failed because one of the column values for the specified alias name had a NULL column name.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
Check the list of column values, and try again with a valid column name.
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.