Nortel Contivity – Cisco 2621

I am trying to establish an IPSEC VPN between a Cisco 2621 and a Nortel Contivity 1010. I am getting most of the way there and then get a debug message on the Cisco saying that it received a unencrypted packet when it should have been encrypted thenthe tunnel falls over. Is the Contivity looking for some additional authentication before it establishes the tunnel?

If anyone has done this before I would be grateful for help.