It looks as if someone has changed the name of the field package_key to package_id, and the datatype from 'character varying' to 'integer', but has not coded the upgrade script to replace the original function.  I presume therefore that the new function is now choking on the field name change.
 public | apm__get_value | character varying | character varying, character varying | stable     | oakmasters | plpgsql  |
                                                                                             |
                   : declare
                   :   get_value__package_key            alias for $1;
                   :   get_value__parameter_name         alias for $2;
                   :   v_parameter_id                    apm_parameter_values.parameter_id%TYPE;
                   :   value                             apm_parameter_values.attr_value%TYPE;
                   : begin
                   :     v_parameter_id := apm__id_for_name (get_value__package_key, get_value__parameter_name);
                   :
                   :     select attr_value into value from apm_parameter_values v
                   :     where v.package_id is null
                   :     and parameter_id = get_value__parameter_id;
                   :
                   :     return value;
                   :
                   : end;
 public | apm__get_value | character varying | integer, character varying           | stable     | oakmasters | plpgsql  |
                                                                                          |
                : declare
                :   get_value__package_id             alias for $1;
                :   get_value__parameter_name         alias for $2;
                :   v_parameter_id                    apm_parameter_values.parameter_id%TYPE;
                :   value                             apm_parameter_values.attr_value%TYPE;
                : begin
                :     v_parameter_id := apm__id_for_name (get_value__package_id, get_value__parameter_name);
                :
                :     select attr_value into value from apm_parameter_values v
                :     where v.package_id = get_value__package_id
                :     and parameter_id = get_value__parameter_id;
                :
                :     return value;
                :
                : end;
(2 rows)