Latest update from Alex at Hamachi staff:

"I got tuncfg+hamachi bundle working, BUT got stuck at something
else. The tunneling device goes up, gets configured, but then
some weird sh*t happens with ARPs. Not sure what's your level of
networking knowledge, but here's a summary -

* say, I ping n770 from my box here over the tunnel

* the ping is successfully de-tunneled and stuffed into tun device
and shortly after that Linux sends an ARP request for my 5.x IP
(this ARP is presumably triggered by n770's pong packet)

* hamachi daemon replies with ARP response, but it appears to be
ignored/discarded by Linux, because it again sends an ARP request

I will have to look at 2.6.16 sources to see what can be causing
this. "

Suggestions anyone?