This is the version of "at" that I have installed:

~ % rpm -qi at
Name        : at                           Relocations: (not relocateable)
Version     : 3.1.8                             Vendor: Red Hat, Inc.
Release     : 13                            Build Date: Thu 14 Dec 2000
08:01:27 PM PST
Install date: Sun 24 Dec 2000 12:53:28 PM PST      Build Host:
porky.devel.redhat.com
Group       : System Environment/Daemons    Source RPM: at-3.1.8-13.src.rpm
Size        : 76060                            License: GPL
Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
Summary     : Job spooling tools.
Description :
At and batch read commands from standard input or from a specified file.
At allows you to specify that a command will be run at a particular time
(now or a specified time in the future).  Batch will execute commands
when the system load levels drop to a particular level.  Both commands
use /bin/sh to run the commands.

You should install the at package if you need a utility that will do
time-oriented job control.  Note: you should use crontab instead, if it is
a recurring job that will need to be repeated at the same time every
day/week/etc.


At some point my system started thrashing a lot and, when I ran ps, I
noticed a lot of atd processes.

My syslog contains many entries of the following form:

Dec 20 10:47:00 altair atd[3874]: File a0007b00f88c5f is in wrong format -
aborting
Dec 20 10:47:00 altair atd[3875]: File a0007c00f88c60 is in wrong format -
aborting
Dec 20 10:47:00 altair atd[3876]: File a0007b00f88c5f is in wrong format -
aborting
Dec 20 10:47:00 altair atd[3877]: File a0007c00f88c60 is in wrong format -
aborting

I will attach an excerpt, later.

This was reproducable every time I (or init) started atd.

I unfortunately do not have the files in question, as I noticed the syslog
spooge much later than I clobbered /var/spool/at