Help, Postgres7.3 --> Postgres7.2.1 database recreation fails

Hello,

I am trying to recreate some database on a Postgres 7.2.1.
The database I developed was on Postgres7.3 because I really needed the
drop column functionality during development.

Now I created a script with pg_dump like this:
(On Postgres 7.3) pg_dump -D mydatabase > mydb.txt

and run it at the Postgres 7.2.1 like this:
psql -d mydatabase -f mydb.txt

It runs fine till it hits this line (and all the next lines that also
set the value for sequences):

SELECT pg_catalog.setval ('tbluser_userid_seq', 11, true);

What is going wrong?
Is there a safe/better way to export a database from 7.3 to 7.2.1 ??

Any help and tips would be greatly appriciated!

Regards,
Erwin