I still have the bug and I have a more recent version of network-manager-pptp (0.7.1~rc4.20090316+bzr23-0ubuntu2). same symptoms: no happy MS-PPTP connection.

this is the log session (some parameters are anonymized) from syslog:
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Apr 15 15:38:30 jackalope-b1 NetworkManager: <info>  Starting VPN service 'org.freedesktop.NetworkManager.pptp'... 
Apr 15 15:38:31 jackalope-b1 NetworkManager: <info>  VPN service 'org.freedesktop.NetworkManager.pptp' started (org.freedesktop.NetworkManager.pptp), PID 4783 
Apr 15 15:38:31 jackalope-b1 NetworkManager: <info>  VPN service 'org.freedesktop.NetworkManager.pptp' just appeared, activating connections 
Apr 15 15:38:31 jackalope-b1 NetworkManager: <info>  VPN plugin state changed: 3 
Apr 15 15:38:31 jackalope-b1 pppd[4787]: Plugin /usr/lib/pppd/2.4.5//nm-pptp-pppd-plugin.so loaded.
Apr 15 15:38:31 jackalope-b1 pppd[4787]: pppd 2.4.5 started by root, uid 0
Apr 15 15:38:31 jackalope-b1 NetworkManager: <info>  VPN connection 'XXXXXXXXXXXX' (Connect) reply received. 
Apr 15 15:38:31 jackalope-b1 pppd[4787]: Using interface ppp1
Apr 15 15:38:31 jackalope-b1 pppd[4787]: Connect: ppp1 <--> /dev/pts/0
Apr 15 15:38:31 jackalope-b1 pptp[4789]: nm-pptp-service-4783 log[main:pptp.c:314]: The synchronous pptp option is NOT activated 
Apr 15 15:38:32 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request' 
Apr 15 15:38:33 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Apr 15 15:38:33 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Apr 15 15:38:33 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request' 
Apr 15 15:38:34 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply.
Apr 15 15:38:34 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 40432). 
Apr 15 15:38:34 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:950]: PPTP_SET_LINK_INFO received from peer_callid 45489
Apr 15 15:38:34 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:953]:   send_accm is 00000000, recv_accm is FFFFFFFF
Apr 15 15:38:34 jackalope-b1 pptp[4799]: nm-pptp-service-4783 warn[ctrlp_disp:pptp_ctrl.c:956]: Non-zero Async Control Character Maps are not supported!
Apr 15 15:38:34 jackalope-b1 pppd[4787]: CHAP authentication succeeded
Apr 15 15:38:35 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:950]: PPTP_SET_LINK_INFO received from peer_callid 45489
Apr 15 15:38:35 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:953]:   send_accm is FFFFFFFF, recv_accm is FFFFFFFF
Apr 15 15:38:35 jackalope-b1 pptp[4799]: nm-pptp-service-4783 warn[ctrlp_disp:pptp_ctrl.c:956]: Non-zero Async Control Character Maps are not supported!
Apr 15 15:38:35 jackalope-b1 pppd[4787]: LCP terminated by peer (t5^R^_^@<M-Mt^@^@^BM-f)
Apr 15 15:38:35 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_disp:pptp_ctrl.c:912]: Received Call Clear Request.
Apr 15 15:38:38 jackalope-b1 pppd[4787]: Connection terminated.
Apr 15 15:38:38 jackalope-b1 NetworkManager: <info>  VPN plugin failed: 1 
Apr 15 15:38:38 jackalope-b1 pppd[4787]: Modem hangup
Apr 15 15:38:38 jackalope-b1 pptp[4789]: nm-pptp-service-4783 warn[decaps_hdlc:pptp_gre.c:204]: short read (-1): Input/output error
Apr 15 15:38:38 jackalope-b1 pptp[4789]: nm-pptp-service-4783 warn[decaps_hdlc:pptp_gre.c:216]: pppd may have shutdown, see pppd log
Apr 15 15:38:38 jackalope-b1 pppd[4787]: Exit.
Apr 15 15:38:38 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[callmgr_main:pptp_callmgr.c:234]: Closing connection (unhandled)
Apr 15 15:38:38 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' 
Apr 15 15:38:38 jackalope-b1 pptp[4799]: nm-pptp-service-4783 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state)
Apr 15 15:38:38 jackalope-b1 NetworkManager: <info>  VPN plugin failed: 1 
Apr 15 15:38:38 jackalope-b1 NetworkManager: <info>  VPN plugin state changed: 6 
Apr 15 15:38:38 jackalope-b1 NetworkManager: <info>  VPN plugin state change reason: 0 
Apr 15 15:38:38 jackalope-b1 NetworkManager: <WARN>  connection_state_changed(): Could not process the request because no VPN connection was active. 
Apr 15 15:38:38 jackalope-b1 NetworkManager: <info>  Policy set 'YYYYYYYYYYY' (ppp0) as default for routing and DNS. 
Apr 15 15:38:50 jackalope-b1 NetworkManager: <debug> [1239802730.001755] ensure_killed(): waiting for vpn service pid 4783 to exit 
Apr 15 15:38:50 jackalope-b1 NetworkManager: <debug> [1239802730.001955] ensure_killed(): vpn service pid 4783 cleaned up 
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what does it means "nm-pptp-service-4783 warn[ctrlp_disp:pptp_ctrl.c:956]: Non-zero Async Control Character Maps are not supported!"???

Thanks a lot
ndv