Locking root account in Ubuntu 8.04 (Hardy) has nasty side effects

When I installed Hardy on my machine, I enabled the root account and then decided to disable it again. I did this by following the instructions I found on the web:

# Enabling the account
$ sudo passwd -u root

# Disabling the account
$ sudo passwd -l root

However, I quickly ran into an issue where the root's cron jobs would not run because the account was locked. After some fiddling, I fixed the problem by first re-enabling the root account:

$ sudo passwd -u root

and then, disabling the account properly:

$ sudo passwd -d root

After this, all works as it should.