[SOLVED] IPv6 not working after Upgrade to 4.1

hello,
i have the same problem after update to proxmox 4.1
the ipv6 address is configured via gui. in /etc/network/interfaces the address show up (address/netmask/gateway) but after reboot no ipv6 address is assigned on the vmbr0.

how can i fix this problem??
Thanks for any help
woodgee