Thanks for your help. Now I'm able to establish a pptp connection as follows:
ppp0 Link encap:Point-to-Point Protocol
inet addr:192.168.0.71 P-t-P:192.168.0.109 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1412 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:13 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:96 (96.0 b) TX bytes:466 (466.0 b)
(seen in the Ubuntu client from the ifconfig command)
Jul 31 19:58:20 server pptpd[587]: CTRL: Client 213.64.16.194 control connection started
Jul 31 19:58:21 server pptpd[587]: CTRL: Starting call (launching pppd, opening GRE)
Jul 31 19:58:21 server pppd[588]: Plugin radius.so loaded.
Jul 31 19:58:21 server pppd[588]: RADIUS plugin initialized.
Jul 31 19:58:21 server pppd[588]: pppd 2.4.4 started by root, uid 0
Jul 31 19:58:21 server kernel: divert: not allocating divert_blk for non-ethernet device ppp0
Jul 31 19:58:21 server pppd[588]: Using interface ppp0
Jul 31 19:58:21 server pppd[588]: Connect: ppp0 <--> /dev/pts/2
Jul 31 19:58:25 server pppd[588]: MPPE 128-bit stateless compression enabled
Jul 31 19:58:25 server pppd[588]: found interface eth0 for proxy arp
Jul 31 19:58:25 server pppd[588]: local IP address 192.168.0.109
Jul 31 19:58:25 server pppd[588]: remote IP address 192.168.0.80
Jul 31 19:58:26 server esmith::event[612]: Processing event: ip-up.pptpd ppp0 /dev/pts/2 460800 192.168.0.109 192.168.0.80 pptpd
Jul 31 19:58:26 server esmith::event[612]: Running event handler: /etc/e-smith/events/actions/generic_template_expand
Jul 31 19:58:26 server esmith::event[612]: expanding /etc/rc.d/init.d/masq
Jul 31 19:58:27 server esmith::event[612]: generic_template_expand=action|Event|ip-up.pptpd|Action|generic_template_expand|Start|1185904706 165416|End|1185904707 786887|Elapsed|1.621471
Jul 31 19:58:27 server esmith::event[612]: Running event handler: /etc/e-smith/events/ip-up.pptpd/S70pptp-interface-access
Jul 31 19:58:28 server /etc/e-smith/events/ip-up.pptpd/S70pptp-interface-access[614]: /home/e-smith/db/configuration: OLD pptpd=service|Interfaces||TCPPort|1723|access|public|sessions|1|status|enabled
Jul 31 19:58:28 server /etc/e-smith/events/ip-up.pptpd/S70pptp-interface-access[614]: /home/e-smith/db/configuration: NEW pptpd=service|Interfaces|ppp0|TCPPort|1723|access|public|sessions|1|status|enabled
Jul 31 19:58:28 server esmith::event[612]: S70pptp-interface-access=action|Event|ip-up.pptpd|Action|S70pptp-interface-access|Start|1185904707 787798|End|1185904708 348183|Elapsed|0.560385
Jul 31 19:58:28 server esmith::event[612]: Running event handler: /etc/e-smith/events/actions/adjust-services
Jul 31 19:58:28 server esmith::event[612]: adjusting non-supervised masq (adjust)
Jul 31 19:58:30 server esmith::event[612]: adjust-services=action|Event|ip-up.pptpd|Action|adjust-services|Start|1185904708 349394|End|1185904710 217094|Elapsed|1.8677
Jul 31 20:01:01 server pptpd[587]: CTRL: Reaping child PPP[588]
Jul 31 20:01:01 server pppd[588]: Modem hangup
Jul 31 20:01:01 server pppd[588]: Connect time 2.6 minutes.
Jul 31 20:01:01 server pppd[588]: Sent 0 bytes, received 1132 bytes.
Jul 31 20:01:01 server pppd[588]: MPPE disabled
Jul 31 20:01:01 server pppd[588]: Connection terminated.
Jul 31 20:01:01 server kernel: divert: no divert_blk to free, ppp0 not ethernet
Jul 31 20:01:03 server esmith::event[816]: Processing event: ip-down ppp0 /dev/pts/2 460800 192.168.0.109 192.168.0.80 pptpd
Jul 31 20:01:03 server esmith::event[816]: Running event handler: /etc/e-smith/events/actions/generic_template_expand
Jul 31 20:01:04 server esmith::event[816]: expanding /etc/rc.d/init.d/masq
Jul 31 20:01:06 server esmith::event[816]: generic_template_expand=action|Event|ip-down|Action|generic_template_expand|Start|1185904863 262261|End|1185904866 451729|Elapsed|3.189468
Jul 31 20:01:06 server esmith::event[816]: Running event handler: /etc/e-smith/events/ip-down/S50isdn-down-notify
Jul 31 20:01:06 server pppd[588]: Exit.
(from messages log in Smeserver)
...but should I really get a net mask of 255.255.255.255???
I think that might be the reason for me being unable to access any other machine in the LAN (including the server itself), or am I missing out on something else?
Any assistance here would be greatly appreciated.