That was what was causing the command to barf :-). Though I still can't get clients on the internal network to grab an IP.
I've tried these various commands based on others recommendations.
ipv6 address 2001:470:880D::1/64
ipv6 nd prefix 2001:470:1F07:3B6::/64 infinite infinite
ipv6 address 2001:470:880D::/64 eui-64
#sh ipv6 int f0/1.2
FastEthernet0/1.2 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::20C:85FF:FE07:A701
Description: $FW_INSIDE$
Global unicast address(es):
2001:470:880D::1, subnet is 2001:470:880D::/64
2001:470:880D:0:20C:85FF:FE07:A701, subnet is 2001:470:880D::/64 [EUI]
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
FF02::1:FF07:A701
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds