SQL & PL/SQL :: Ora-04062 Timestamp Changed

I had follwoing function

Create Or Replace Function Fin_Prd(V_Dte In Date) Return Number Is
V_Fin_Str Number;
Begin

[Code].....

The above function was running well. Today i have made some change as under

Create Or Replace Function Fin_Prd(V_Dte In Date,V_Rtn_Flg In Number Default 0) Return Number Is
V_Fin_Str Number;

[Code]....

Above function is created and working well when i use it in query in sql prompt or Toad. But problem is this that all function which used this are invalid and when i run report whose query use FIN_PRD then error is "Ora-04062. Timestamp of Fin_Prd has been changed".