[PERFORM] not exists clause

[S Golly]

I cannot get the "not exists" clause of ANSI SQL to execute correctly.
select t.col11, t.col1... from table1 t where not exists (select 1 from
table2 where col2 = t.col1);
table1 has 40M + rows. if that matters.

OS is FreeBSD 6.2, postgresql version 8.2.6

Is it not supported or a bug ?
thank you for your support.