IP Alias

[IsomerX]

I'm trying to create an IP address alias for the network card on one of 
y servers.  It is running Ubuntu 6.9.

I have the following lines in my /etc/network/interfaces:

auto eth1

iface eth0 inet static
address 192.168.0.98
netmask 255.255.255.0
gateway 192.168.0.1

iface eth1:0 inet static
address 192.168.1.100


When I issue the command ifconfig eth1:0 up I get the following error:
SIOCSIFFLAGS: Cannot assign requested address

When I add this line:

auto eth1:0

to /etc/network/interfaces and reboot the system the network comes up, 
but the alias isn't configured.

I want the alias to configure automatically on boot, what am I doing wrong?

IsomerX