Do you know what type of authentication the Pix is configured for remote access VPN Users. If you are using Internal Authentication or External Authentication like Radius, etc., make sure that the username/password that you are using exist on the auth server.
If you do not want to authenticate the users, then make sure that the Pix is not configured for VPN Remote Access User Authentication.
If you have configured the Pix for internal authentication, make sure that you are using the username password that you configured. If you are still having issues, can you post the configuration from the pix.
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...