connection form vm to the internet impossible

Hello
i succed in the installation of proxmox 3.0 on my server with 2 physical network card (eth0 and eth1).
i install the first VM in bridge mode (on eth0) and use vmbr0, no problem, i can ping, update the OS.
But now i want to install a second VM and use vmbr1 again in bridge mode (on eth0) and now ping to the internet, update the os is impossible.
here is my /etc/network/interfaces of my server. Can you explain to me where is the mistake?
for the moment i don t want to use eth1, in the futur i will install other VM and put it in bridge mode on eth1

auto lo
iface lo inet loopback

iface eth0 inet manual
iface eth1 inet manual

auto vmbr0
iface vmbr0 inet static
address 1.2.3.4
netmask x.x.x.x
gateway a.a.a.a
bridge_ports eth0
bridge_stp off
bridge_fd 0

auto vmbr1
iface vmbr1 inet static
address 1.2.3.5
netmask x.x.x.x
gateway a.a.a.a
bridge_ports eth0
bridge_stp off
bridge_fd 0

auto vmbr2 ###in the futur
iface vmbr2 inet static
address 1.2.3.6
netmask x.x.x.x
gateway a.a.a.a
bridge_ports eth1
bridge_stp off
bridge_fd 0

best regard
oliver