shmctl EIDRM preventing startup

One of the servers I use (RHEL AS 4; Linux 2.6.9-34.ELsmp x86_64)
appears to be in the same state after a reboot as the server in the
"Restart after poweroutage" thread from a few months ago:

http://archives.postgresql.org/pgsql-general/2007-03/msg00738.php

As in the thread, "ipcs -a" shows no postgres-owned shared memory
segments and strace shows shmctl() failing with EIDRM.

http://archives.postgresql.org/pgsql-general/2007-03/msg00743.php

I have only limited access to the box and I haven't found out why
it was rebooted.  I don't think it was a scheduled reboot so it
might have been due to a power outage.

Has anybody figured out if this is a Linux kernel bug?  I might
have until Monday morning if anybody can suggest something to look
at; after that the admins will probably reboot and/or remove
postmaster.pid to get the database running again.

Thanks.

--
Michael Fuhr