For some reason (which I haven't been able to determine yet), yesterday morning the networking service on our web server (running Ubuntu 8.04.2 LTS -- hardy) wouldn't start, and our website went down.

I noticed the following error message when trying to restart it:

* Reconfiguring network interfaces...
/etc/network/interfaces:6: option with empty value
ifup: couldn't read interfaces file "/etc/network/interfaces"
   ...fail!

Line 6 in the /etc/network/interfaces file concerned a MODPROBE command, which (I believe) loaded in the ip_conntrack_ftp module so that I could use PASV on my FTP server (vsftpd): (breaking modprobe commands commented out below)

# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
# /usr/share/doc/ifupdown/examples for more information.
# The loopback network interface
auto lo
iface lo inet loopback
#MODPROBE=/sbin/modprobe
#$MODPROBE ip_conntrack_ftp
pre-up iptables-restore < /etc/iptables.up.rules

# The primary network interface
# Uncomment this and configure after the system has booted for the first time
auto eth0
iface eth0 inet static
    address xxx.xxx.xxx.xxx
    netmask 255.255.255.0
    gateway xxx.xxx.xxx.1
    dns-nameservers xxx.xxx.xxx.4 xxx.xxx.xxx.5

I've verified that there is a file in /sbin called modprobe.

Like I said earlier, this setup had been working flawlessly until yesterday morning (though my bosses say that the site actually went down the previous night at 11 PM EST).

Can anyone shed some light on (A) why this broke, and (B) how can I re-enable the ip_conntrack_ftp module?