[CentOS] Strange problem with filesystem changes reverting on reboot

Our sysadmin was doing midnight work on moving some hardware to new
power outlets.  We'd recently done a CentOS 5.3 install on one of
those machines and then "yum install" with the centosplus kernel and
some rpmforge packages.  It had been up and running fine for at least
two weeks in that configuration.  He sent this message:

On reboot the root file system seems to have reverted to the previous
startup -- no CentOS plus, no Dag repository info in /etc/yum.repos.d,
no xfs, and therefore no /var/lib/mysql.  This is at least the second
time we've experienced this phenomenon ... suffice to say I am really
really suspicious about ext3 now.

The previous time this occurred was quite some time ago, probably soon
after the CentOS 5.1 release -- we'd written it off as pilot error of
some kind.  The root is not an LVM, but it is on a software RAID -- my
suspicion leans more toward a RAID issue than ext3.

Does any of this sound familiar to anyone?