Solaris 10: crontab ignored for user? "! bad user ()" in Log?

Just had a problem about a crontab not being executed for a system user. In /var/cron/log the message

! bad user (cyrus) Mon May  9 08:05:00 2011

shows up.

The cure was simple: The system user "cyrus" had a locked password in /etc/shadow:

cyrus:*LK*:::::::

Cron does not like this. Just set a random password for the user and throw it away. Damn. Solaris 10 Cron does not work with "locked password"-Users.