(usagi-users 03479) traceroute6 fails on 1 (2) machine

I have set up IPv6 on my home network and it almost works. For some reason one 
of the machines cannot do traceroute6.

Network topology:
  Net 1 (2001:: and fec0::1....)
    _: ipv4 router (cisco stuff, not important)
    B: IPv6 router via tunnel broker (Suse 9.3, kernel 2.6.11.4-21.8-default)
    C: workstation (Suse 9.3, kernel 2.6.11.4-21.8-smp)
    D: fileserver (redhat 8, kernel 2.4.18-4)
    E: other server (suse 7.3, kernel 2.2.19)
  Net 2 (fec0::1...)
    C: workstation (Suse 9.3, kernel 2.6.11.4-21.8-smp)
    D: fileserver (redhat 8, kernel 2.4.18-4)

"ping6 www.kame.net" works on all machines.
"telnet 2001:200:0:8002:203:47ff:fea5:3085 80" works too on all machines.
"traceroute6 -n -N 1 -q 1 www.kame.net" works on all machines EXCEPT C

I have checked the routing tables, radvd configuration, firewall settings, 
etc. I cannot find the error.

When doing a traceroute6 on machine C I get this from ethereal:
---snip---
No.     Time        Source                Destination           Protocol Info
      1 0.000000    2001:618:400:5fd6:20c:76ff:fe6d:bc83 
2001:200:0:8002:203:47ff:fea5:3085 UDP      Source port: 64000  Destination 
port: traceroute

No.     Time        Source                Destination           Protocol Info
      2 0.001225    2001:618:400:5fd6:200:24ff:fec4:cbf8 ff02::1:ff6d:bc83     
ICMPv6   Neighbor solicitation

No.     Time        Source                Destination           Protocol Info
      3 0.001292    2001:618:400:5fd6:20c:76ff:fe6d:bc83 
2001:618:400:5fd6:200:24ff:fec4:cbf8 ICMPv6   Neighbor advertisement

No.     Time        Source                Destination           Protocol Info
      4 0.001516    2001:618:400:5fd6:200:24ff:fec4:cbf8 
2001:618:400:5fd6:20c:76ff:fe6d:bc83 ICMPv6   Time exceeded (In-transit)

No.     Time        Source                Destination           Protocol Info
      5 4.998787    fe80::20c:76ff:fe6d:bc83 fe80::200:24ff:fec4:cbf8 ICMPv6   
Neighbor solicitation

No.     Time        Source                Destination           Protocol Info
      6 4.999164    fe80::200:24ff:fec4:cbf8 fe80::20c:76ff:fe6d:bc83 ICMPv6   
Neighbor advertisement

No.     Time        Source                Destination           Protocol Info
      7 4.999895    fe80::20c:76ff:fe6d:bc83 
2001:618:400:5fd6:200:24ff:fec4:cbf8 ICMPv6   Neighbor solicitation

No.     Time        Source                Destination           Protocol Info
      8 5.000217    2001:618:400:5fd6:200:24ff:fec4:cbf8 
fe80::20c:76ff:fe6d:bc83 ICMPv6   Neighbor advertisement

No.     Time        Source                Destination           Protocol Info
      9 9.998216    fe80::200:24ff:fec4:cbf8 fe80::20c:76ff:fe6d:bc83 ICMPv6   
Neighbor solicitation

No.     Time        Source                Destination           Protocol Info
     10 9.998236    fe80::20c:76ff:fe6d:bc83 fe80::200:24ff:fec4:cbf8 ICMPv6   
Neighbor advertisement
---snip---

And then traceroute6 hangs indefinitely.

I don't get it. I have looked at the routing tables, radvd configuration, 
interface configuration, firewall settings (yes, checked the drop counters 
too). I cannot find anything wrong.

Can anyone point me in the right direction?