create of partition table slow

Why does the following statement take very long

create table child_table_2009_08_01(check (datefield >= '2009-08-01
00:00:00' and datefield < '2009-08-02 00:00:00')) inherits
(parent_table)

Note that this is the first partition for the month of August.
Subsequent partitions are created very quickly.

There are about 15 existing partitions already present for the parent
table. I would expect create table to be lightning fast...is there
more to the create partitioned table than meets the eye.

There are no concurrent accesses to the table. I disable all remote
and local connections so that only the create partitions script runs.

Postgres version 8.1.2 running on Dell 2850 Raid 10(4x300G disks)
RHEL 3 2.4.21-37.ELsmp