Referential integrity Freeze

Hello,

I have two 4 table with referential constraint's that are hanging when I
try to delete from them.

I have a,
users table, ( 30000 rows )
suburbs table ( 16000 rows ),
regions table ( 54 rows )and
a bus_pc_idc table ( business type ) ( 30000 rows )

Here is my integrity rules:

create table bus_pc_idc (
id serial,
user_id int4 REFERENCES users(user_id) ON DELETE CASCADE ON
UPDATE CASCADE NOT NULL,
sub_id int4 REFERENCES suburbs(sub_id) ON DELETE CASCADE ON
UPDATE CASCADE NOT NULL,
idc_id int4 REFERENCES idc(id) ON DELETE CASCADE ON UPDATE
CASCADE NOT NULL,
active bool NOT NULL DEFAULT 'f'::bool
);

As the system is still being developed I want to 'empty' out the
database from titme to time and rebuild it.
I think that when I delete from the users table the delete should
cascade through the bus_pc_idc table.
However it's justing hanging when I delete all from the users table.
When the database is hanging the CPU is 99% for the Postgres process.

I can't see what's wrong. Perhaps I'm missing something in the
referential integrity.
Thanks in advance
Cheers
Rudi.