ORA-06502 error when returning varchar2...

I have an procedure with an query like:

function aa() return varchar2 as

begin
update table1

   set field_1='xxx'
  where id=1
 returning field_2 into v_retval:

return v_retval;
end;

I'm handling that simple function in vb.net 2005. But, in vb.net I receive an ORA 6502 error.. why? fileld size is not a problem. Received on Sat Mar 08 2008 - 16:42:40 CST