Oracle Error Message
PLS-00905: object string is invalid
Reason for the Error
An invalid package specification or stored subprogram was referenced. A package specification or stored subprogram is invalid if its source code or any database object it references has been DROPped, REPLACEd, or ALTERed since it was last compiled.
Solution
Find out what invalidated the package specification or stored subprogram, then make sure that Oracle can recompile it without errors.