6to4 suddenly stopped working to 2001: addresses

[Pete French]

I've got three installations of FreeBSD using 6to4 in three different
physical locations, attached to three different ISPs. Sometime in the last
few days all of them have stopped talking to IPv6 addesse which are
not also 6to4. I can still talk to 2002: addresses, but not to 2001:
addresses.

This all worked fine a few days ago, and nothing has changed in the config of
any of these machines. I can ping 192.88.99.1 under IPv4, so I should
have a route to 2002:c390:806::, but traceroute6 to anything not in
2002: doesnt show any hops, and I cannot connect to any of these sites.

Can anyone shed any light on this ? It hardly seems likely that theres
been some massive failure of 6to4 in the London area, but I can't
see any reason why all of this would have suddenly stopped working.

-pete.