[tlug] broken cron?

[Sven Simon <sven@example.com>]

Sorry, it's a FreeBSD question, but since many of you are running some *BSD
distro I hope I could find some help, anyway.
Since recently, I get every five minutes a message in root's mail like this:

 From root Sun Mar 24 00:55:00 2002
Date: Sun, 24 Mar 2002 00:55:00 +0900 (JST)
From: root (Cron Daemon)
To: root
Subject: Cron <root@example.com> root /usr/libexec/atrun
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin>
X-Cron-Env: <HOME=/root>
X-Cron-Env: <LOGNAME=root>
X-Cron-Env: <USER=root>

root: not found

Now, my crontab says that atrun will run every five minutes, but I never 
got that mail
before and even more suspicious is this "root: not found" thing.
In syslog it shows up as:
Mar 24 00:55:00 [nodename] /usr/sbin/cron[1201]: (root) CMD 
(root^I/usr/libexec/atrun)

Does anybody know what wrong? Where should I dig around other than crontab?

Sven