After installing a database sometimes sys objects are invalid, and don't recompile. In this case you have to use the script utlrp.sql. You can find this script on the database-machine in the RDBMS-directory where the oracle-software is installed for example C:\oracle\product\10.2.0\db_1\RDBMS\ADMIN. These scripts sometimes don't work with sql-tools. So i prefer to use plain SQLPLUS on the machine directly. Just connect as SYS and execute the scripts like this:

• cd C:\oracle\product\10.2.0\db_1\RDBMS\ADMIN
  
• SET ORACLE_SID=STRANGEDATABASE 

• sqlplus sys/change_on_install as sysdba
  
• start utlrp.sql