It seems that a part of my mail reply was lost by the post office ^^ Here it is again, full size :)

So here is the /var/log/messages output  when attempting to connect using vpn.iprdator.se instead of ip address 

Jan  9 20:10:24 doki-desktop pppd[3979]: Plugin /usr/lib/pppd/2.4.5//nm-pptp-pppd-plugin.so loaded.
Jan  9 20:10:24 doki-desktop pppd[3979]: pppd 2.4.5 started by root, uid 0
Jan  9 20:10:24 doki-desktop pppd[3979]: Using interface ppp0
Jan  9 20:10:24 doki-desktop pppd[3979]: Connect: ppp0 <--> /dev/pts/1
Jan  9 20:10:26 doki-desktop pppd[3979]: CHAP authentication succeeded
Jan  9 20:10:26 doki-desktop pppd[3979]: MPPE 128-bit stateless compression enabled
Jan  9 20:10:26 doki-desktop pppd[3979]: local  IP address 93.182.181.186
Jan  9 20:10:26 doki-desktop pppd[3979]: remote IP address 93.182.181.2
Jan  9 20:10:26 doki-desktop pppd[3979]: primary   DNS address 93.182.182.85
Jan  9 20:10:26 doki-desktop pppd[3979]: secondary DNS address 93.182.182.85
Jan  9 20:11:06 doki-desktop pppd[3979]: Terminating on signal 15
Jan  9 20:11:06 doki-desktop pppd[3979]: Connect time 0.7 minutes.
Jan  9 20:11:06 doki-desktop pppd[3979]: Sent 0 bytes, received 11313 bytes.
Jan  9 20:11:06 doki-desktop pppd[3979]: Child process /usr/sbin/pptp vpn.ipredator.se --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-3976 (pid 3981) terminated with signal 15
Jan  9 20:11:06 doki-desktop pppd[3979]: Connection terminated.
Jan  9 20:11:06 doki-desktop pppd[3979]: Exit.

And /var/log/daemon :

Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> Starting VPN service 'org.freedesktop.NetworkManager.pptp'...
Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> VPN service 'org.freedesktop.NetworkManager.pptp' started (org.freedesktop.NetworkManager.pptp), PID 3976
Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> VPN service 'org.freedesktop.NetworkManager.pptp' appeared, activating connections
Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> VPN plugin state changed: 1
Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> VPN plugin state changed: 3
Jan  9 20:10:24 doki-desktop NetworkManager[1497]: <info> VPN connection 'Connexion VPN 1' (Connect) reply received.
Jan  9 20:10:24 doki-desktop modem-manager: (net/ppp0): could not get port's parent device
Jan  9 20:10:24 doki-desktop NetworkManager[1497]:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Jan  9 20:10:24 doki-desktop NetworkManager[1497]:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Jan  9 20:10:24 doki-desktop pptp[3983]: nm-pptp-service-3976 log[main:pptp.c:314]: The synchronous pptp option is NOT activated
Jan  9 20:10:24 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
Jan  9 20:10:24 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Jan  9 20:10:24 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Jan  9 20:10:25 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
Jan  9 20:10:25 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply.
Jan  9 20:10:25 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 28672).
Jan  9 20:11:05 doki-desktop NetworkManager[1497]: <warn> VPN connection 'Connexion VPN 1' (IP Config Get) timeout exceeded.
Jan  9 20:11:06 doki-desktop NetworkManager[1497]: <info> Policy set 'Auto eth0' (eth0) as default for IPv4 routing and DNS.
Jan  9 20:11:06 doki-desktop avahi-daemon[1466]: Withdrawing workstation service for ppp0.
Jan  9 20:11:06 doki-desktop NetworkManager[1497]:    SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Jan  9 20:11:06 doki-desktop pptp[3983]: nm-pptp-service-3976 warn[decaps_hdlc:pptp_gre.c:204]: short read (-1): Input/output error
Jan  9 20:11:06 doki-desktop pptp[3983]: nm-pptp-service-3976 warn[decaps_hdlc:pptp_gre.c:216]: pppd may have shutdown, see pppd log
Jan  9 20:11:06 doki-desktop pptp[3997]: nm-pptp-service-3976 log[callmgr_main:pptp_callmgr.c:234]: Closing connection (unhandled)
Jan  9 20:11:06 doki-desktop pptp[3997]: nm-pptp-service-3976 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
Jan  9 20:11:06 doki-desktop pptp[3997]: nm-pptp-service-3976 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state)

Then same using ip address, which is working: 

/var/log/messages :

Jan  9 20:18:35 doki-desktop pppd[4057]: Plugin /usr/lib/pppd/2.4.5//nm-pptp-pppd-plugin.so loaded.
Jan  9 20:18:35 doki-desktop pppd[4057]: pppd 2.4.5 started by root, uid 0
Jan  9 20:18:35 doki-desktop pppd[4057]: Using interface ppp0
Jan  9 20:18:35 doki-desktop pppd[4057]: Connect: ppp0 <--> /dev/pts/1
Jan  9 20:18:37 doki-desktop pppd[4057]: CHAP authentication succeeded
Jan  9 20:18:37 doki-desktop pppd[4057]: MPPE 128-bit stateless compression enabled
Jan  9 20:18:40 doki-desktop pppd[4057]: local  IP address 93.182.181.211
Jan  9 20:18:40 doki-desktop pppd[4057]: remote IP address 93.182.181.2
Jan  9 20:18:40 doki-desktop pppd[4057]: primary   DNS address 93.182.182.85
Jan  9 20:18:40 doki-desktop pppd[4057]: secondary DNS address 93.182.182.85


/var/log/daemon : 

Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> Starting VPN service 'org.freedesktop.NetworkManager.pptp'...
Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> VPN service 'org.freedesktop.NetworkManager.pptp' started (org.freedesktop.NetworkManager.pptp), PID 4054
Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> VPN service 'org.freedesktop.NetworkManager.pptp' appeared, activating connections
Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> VPN plugin state changed: 1
Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> VPN plugin state changed: 3
Jan  9 20:18:35 doki-desktop NetworkManager[1497]: <info> VPN connection 'Connexion VPN 1' (Connect) reply received.
Jan  9 20:18:35 doki-desktop modem-manager: (net/ppp0): could not get port's parent device
Jan  9 20:18:35 doki-desktop NetworkManager[1497]:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Jan  9 20:18:35 doki-desktop NetworkManager[1497]:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Jan  9 20:18:35 doki-desktop pptp[4061]: nm-pptp-service-4054 log[main:pptp.c:314]: The synchronous pptp option is NOT activated
Jan  9 20:18:35 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
Jan  9 20:18:36 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Jan  9 20:18:36 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Jan  9 20:18:36 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
Jan  9 20:18:37 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply.
Jan  9 20:18:37 doki-desktop pptp[4075]: nm-pptp-service-4054 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 31232).
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> VPN connection 'Connexion VPN 1' (IP Config Get) reply received.
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: nm_ip4_config_add_nameserver: assertion `nameserver != s' failed
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> VPN Gateway: 93.182.181.2
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Tunnel Device: ppp0
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Internal IP4 Address: 93.182.181.211
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Internal IP4 Prefix: 32
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Internal IP4 Point-to-Point Address: 93.182.181.2
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Maximum Segment Size (MSS): 0
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> Internal IP4 DNS: 93.182.182.85
Jan  9 20:18:40 doki-desktop NetworkManager[1497]: <info> DNS Domain: '(none)'
Jan  9 20:18:41 doki-desktop NetworkManager[1497]: <info> VPN connection 'Connexion VPN 1' (IP Config Get) complete.
Jan  9 20:18:41 doki-desktop NetworkManager[1497]: <info> Policy set 'Connexion VPN 1' (ppp0) as default for IPv4 routing and DNS.
Jan  9 20:18:41 doki-desktop NetworkManager[1497]: <info> VPN plugin state changed: 4
Jan  9 20:18:41 doki-desktop nm-dispatcher.action: Script '/etc/NetworkManager/dispatcher.d/01ifupdown' exited with error status 1.

Just ask if you need more tests to be done, or I can just provide you with my VPN Credentials, as I just bought a 3 months subscriptions just to have this bug clarified ^^

Aurélien