Page header error on PGSQL 7.4.5

We have PostgreSQL v. 7.4.5 and main application
working with PGSQL via libpq.
Linux kernel 2.6.17.14

We encounter page header error occasional occurence in
different tables, including system pg_xxx.

Database is restored transactionally using restore.sql commands:

drop table ..., create table ... , copy ... from ...

from night dump automatically and we have no problems.

Equipment: processor ST sh4-7100, RAM 128 MB.

Disk partition size where the PostgreSQL is installed, is of 100 GB.

Cluster size is about 90 MB.

We have about a hundred of computer with similar configuration.

On most of them the error doesn't appear for months, even when the equipment
is rather carelessly operated including power interruption without
due termination of PostgreSQL work.

We have installed PostgreSQL 8.2.5 on several test devices, and the error didn't appear,
but the test period was rather short.

After all this we are considering the necessity of moving to the latest version
of PostgreSQL, since the page header error also appeared under its version 8.3.1
with OS FreeBSD 7.0 :

http://www.sql.ru/forum/actualthread.aspx?tid=558969&hl=page+header

Thank You!