Final follow-up: Exactly the same configuration of poptop but with kernel-2.4.7 works fine. Must be a change in the ipv4 implementation in 2.4.8 or 2.4.9 that affects poptop. pptp-client on 2.4.9 connects to poptop on 2.4.7 without a problem. Just a heads-up in case anyone is thinking of upgrading to 2.4.8 or 2.4.9. Martin.