Its interesting as it simply fails to establish. And Interestingly I've seen a session on the other end (ASA) which shows the connection as a user connection and using encryption /hash thats not configured.
Try to clear the crypto sessions on the router doesn't help.
Interesting you brought up the ASA. I have an ASA running 8.0(2)that will just not make a vpn connection. What version is the ASA? and is your config easy vpn in network extension mode or pure lan to lan vpn.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...