database corruption

For several weeks now we have been experiencing fairly
severe database corruption upon clean reboot. It is very
repeatable, and the corruption is of the following forms:

ERROR: could not access status of transaction foo
DETAIL: could not open file "bar": No such file or directory

ERROR: invalid page header in block foo of relation "bar"

ERROR: uninitialized page in block foo of relation "bar"

At first, we believed this was related to XFS, and have
been pursuing investigations along those lines. However,
we have now experienced the exact same problem with JFS.

Here are some details:

- Postgres 7.4.2
- 2.6.6 kernel.org kernel
- dedicated database partition
- repeatable with XFS and JFS (have not seen on ext3)
- repeatable with and without Linux software RAID 0
- repeatable with IDE and SATA
- repeatable with and without fsync, and with fdatasync
- repeatable on multiple systems

I have two questions:

- any known reason why this might be occurring? (we must
have something wrong, for this high rate of severe
error).

- if I don't care about losing data, and am not interested
in trying to recover anything, how can I arrange for
Postgres to proceed normally? I know about
zero_damaged_pages, but this doesn't help with missing
transaction files and such. Is there any way to get
Postgres to chuck anything bad and proceed?

Thanks,

--Ian