[Gloucs] Using host networking and NAT with VirtualBox

[Sean]

Hope someone can help!!!!!!!!!!!!!!!!!!

I've just upgraded from ubuntu 11.10 to 12.04

I use Virtualbox....
to isolate all my virtualbox setups I have created in the past a Host network with NAT by installing 
Bridge-utils ..... and adding in /etc/network/interfaces
...

auto vnet0
iface vnet0 inet static
        address 172.16.0.1
        netmask 255.255.255.0
        bridge_ports none
        bridge_maxwait 0
        bridge_fd 1
        up iptables -t nat -I POSTROUTING -s 172.16.0.0/24 -j MASQUERADE
        down iptables -t nat -D POSTROUTING -s 172.16.0.0/24 -j MASQUERADE

Also in editing /etc/sysctl.conf   ...edit to allow 
net.ipv4.ip_forward=1

Now.......................
I have never had a problem with with 11.04 or 11.10 but somehow the Ubuntu ufw firewall in 12.04 blocks any NAT through to my "vnet0" regardless of what I try do do....

HELP!   any ideas

Regards
Sean