Windows Vista Teredo status: "general system failure"

A friend's Windows Vista machine is showing an ugly Teredo status: "general system failure". Needless to say: Teredo is not working. There's even no 2001:0: address. There is, however, strangely enough, a 6to4 2002:-address ...

I don't know what the cause is. It might be related to his firewall. He's not behind NAT.

Comments / tips welcome.


C:\Users\Alain>netsh interface teredo show

The following commands are available:

Commands in this context:
show state     - Shows Teredo state.

C:\Users\Alain>netsh interface teredo show state
Teredo Parameters
---------------------------------------------

Type                    : default
Server Name             : teredo.ipv6.microsoft.com.
Client Refresh Interval : 30 seconds
Client Port             : unspecified
State                   : offline
Error                   : general system failure


C:\Users\Alain>


C:\Users\Alain>ping 2001:4de0:1::1:1

Pinging 2001:4de0:1::1:1 from 2002:5ed1:bd57::5ed1:bd57 with 32 bytes of data:
General failure.
General failure.
General failure.
General failure.

Ping statistics for 2001:4de0:1::1:1:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

C:\Users\Alain>