Anyway, I'll compile a vpnc binary where IKE_ATTRIB_LIFE_DURATION = 3600 (instead of 2147483) and draft-ietf-ipsec-nat-t-ike-03 code is patched in place of draft-ietf-ipsec-nat-t-ike-02. Whenever I get it done I put it avalable somewhere -- let's hope that is enough to solve this issue.