>For testing purposes I need to generate the error consistently.

Dan,
Taken from the Fox Wiki:

create table Clients ( iClKey i )
create table Orders ( iOdKey i, iOdClKey i )
select * ;
from clients ;
left join orders on iClKey = iOdClKey ;
where isnull( iOdKey ) or iOdkey in ( select min( iOdKey ) from orders )

will C5 VFP even with SP3 installed.

HTH.