SQL and parse errors

Howdy:

Running Postgres 7.1.3 on RedHat Linux 7.2, kernel 2.4.7-rel 10.

Have an SQL question, which may very well be that
I need a second pair of eyes to trouble shoot the script.

[script]
explain
select
                q.qid,
                q.year,
                m.contract,
                m.mbr_num,
                m.bu,
                m.mbr_sex,
                m.product,
                m.prov_num,
                m.riskgrp,
                p.c_spec_1 as spec,
                date_larger(m.effdt, q.effdt) as effdt,
                date_smaller(m.enddt, q.enddt) as enddt,
        -->>>   (date_smaller(m.enddt, q.enddt) as enddt - date_larger(m.effdt, q.effdt) as effdt)::float8 / 30.4 as memmonth <<<--

        from    members m,
                product p,
                quarters q
        where
m.prov_num=p.c_prov_num

        --------- make sure *all* the spans overlap one another ----
          and not (
                m.enddt < q.effdt
                or m.effdt > q.enddt
                )
;
[/script]

I believe the problem comes from what's marked off by
the arrows.  The error I get from this is:

ERROR:  parser: parse error at or near "as"

If I comment that out, things work.  It *used* to work
before, but for the life of me, I don't recall changing
anything ...

Where is the syntax error?

Thanks!

-X