ORA700 error on plsql execution

Hi,

My application is hitting those errors :

ORA-00700: erro soft interno, argumentos: [kgegpa:parameter corruption], [], [], [], [], [], [], [], [], [], [], []

And we could debug it up to this sort of code ;

variable := to_char ( myPackage.proc1 (val1, val2)) ;

and myPackage code is returning "null" value :

begin 
...
if sometest = 0 
then return null ;
end if;
...
end;

My question is : does it makes sense to raise ORA700 error ?

This only occurs at production box, which is a 4 node RAC install, dev and qa boxes do not show any problem. Also, myPackage is a core application component, so it is executed all day, all the time.

Please share your thoughts. thanks!