Fail of a return query from plpgsql function for a specific table

CREATE OR REPLACE FUNCTION uf_testfunction()

  RETURNS SETOF associates AS

$BODY$

begin 

return query select * from associates;

return;

end;

$BODY$

  LANGUAGE 'plpgsql' VOLATILE;

This works fine for above table but not works at all for accgroups table. As I searched for this over web, it is identified as a bug for tables whose columns are changed(deleted and added). Is it true? 

How to solve this issue?

Thanks

CPK