Anyone got IPv6 working via SixXS.net?

Hi all,

I'm trying to get an IPv6 link going to sixxs.net.

I've followed the wiki howto found here 
https://www.sixxs.net/wiki/Configuring_MonoWall but I cannot raise the link.

When I do an ifconfig -a via /exec.php I get this for gif0 so it looks 
like something is happening;

gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
	tunnel inet 173.63.170.47 --> 66.117.47.228
	inet6 fe80::202:e3ff:fe44:1b5e%gif0 prefixlen 64 scopeid 0x18
	inet6 2001:4830:1600:277::2 --> 2001:4830:1600:277::1 prefixlen 128
	inet6 2001:4830:1600:278::2 --> 2001:4830:1600:278::1 prefixlen 128


If I transfer the settings to my winXP box I get a successful tunnel and 
can stream audio from the University of Southampton's IPv6 media server 
without issue.

Using 
http://www.subnetonline.com/pages/ipv6-network-tools/online-ipv6-ping.php I 
cannot ping my end of the tunnel on monowall but can on my XP machine.

ping6 2001:4830:1600:277::1 from monowall to the ISP fails suggesting 
that the link is not up.

I have both LAN and WAN IPv6 rules set to allow ping to the v6 WAN 
address and and "all-star" rule to allow any to any.

I don't have any v6 addresses yet. sixxs won;t give me any until my link 
has been up for a while and I've enough credits to pay for it.

Any ideas?

Thanks

Mark