Hi,
I have static networking for IPv4 setup as follows on Ubuntu 10.04 LTS and all is working well.

auto lo
iface lo inet loopback

auto eth0 eth0:0

iface eth0 inet static
address <address here>
netmask 255.255.255.0
gateway <address here>

iface eth0:0 inet static
address <address here>
netmask 255.255.255.0
gateway <address here>

For IPv6 I added the following:

iface eth0 inet6 static
address <IPv6 main address>
netmask 64
gateway fe80::1
up ip -f inet6 addr add <IPv6 address 1>/64 dev eth0
up ip -f inet6 addr add <IPv6 address 2>/64 dev eth0
up ip -f inet6 addr add <IPv6 address 3>/64 dev eth0

On reboot this works fine and when I do a networking restart it works for a little while and then I start getting this:

* Reconfiguring network interfaces...
SIOCADDRT: File exists
Failed to bring up eth0.
ssh stop/waiting
ssh start/running, process 13580

All the IPv4 addresses are up on eth0 and the virtual interface and the main IPv6 address also comes up on eth0 but the three addresses for the IPv6 range don't. This appears random.

Any thoughts?