Postres dilemma

Hi

I am using Postgres 7.3.4 over linux Redhat 7.3 on
i686 machine.

My app has one parent table and five child tables. I
mean the parent table has a primary key and child
tables have foreign key relationship with parent.
My App is doing 500 inserts initially in each table.
After all this done, we inserting 50 in each table and
deleting previous 50 records every seconds. System
performs well for awhile (<30 Hrs). After 30 hrs I
seen that dir size of $PGDATA/base dir is keep on
growing and to goes up to 2G in 48 hrs. App is also
doing vacuum every 45 seconds. Every time vacuum is
triggered, the system goes extreamly slugginsh, and
results in various errors like deadlock
detected(confirmed in the $PGDATA/../LOG/logfile).
vmstat is also showing that blocks sents to the block
device (disk) is going crazy.
I do not know what is the remedy for this problem. If
someone has come across to the issue, please help me
as soon as possible.
++++++++++++++++++++++++++++++++++++++++++++++++++
NOTE: I can not use Postgres 7.4 and higher releases
beacuse postmaster crashes gauranteed in (20hrs). I
have already reported this bug many times (Bug # 1104
is one of them). All crashes show the same behavior
and error messages.
(specified item offset is too large)
++++++++++++++++++++++++++++++++++++++++++++++++++

I appreciate if some one have the solution for my
problem. otherwise it looks like all our app
development done on top of Postgres is going in vain.

Thanking you in advance.

Neeraj K Sharma
email: neeraj(dot)sharma(at)arroyo(dot)tv
neerajsharma(at)hotmail(dot)com