pptp disconnect when get some info

i try ubuntu 6.06 / 6.10 / 7.10

i have 4 ubuntu vpn server
server options
/etc/pptpd.conf

speed 230400
noipparam
localip 192.168.15.1
remoteip 192.168.15.10-20
#listen 192.168.0.3
option /etc/ppp/pptpd-options
logfile /var/log/pptpd1.log

/etc/ppp/pptpd-options

name pptpd
mtu 1490
mru 1490
require-chap
refuse-pap
refuse-eap
refuse-mschap
refuse-mschap-v2
proxyarp
nodefaultroute
lock
nobsdcomp
logfile /var/log/pptpd.log
# debug
lcp-echo-interval 0
lcp-echo-failure 0

when i connect from windows all work nice, but when i connect from ubuntu some time i get disconnect
client option

/etc/ppp/peers/rv

name at
remotename rv
linkname rv
ipparam rv
lock
noauth
nobsdcomp
nodeflate
#updetach
nodetach
noproxyarp
pty "pptp rv....net --nolaunchpppd"
lcp-echo-failure 30
lcp-echo-interval 5
#debug
#usepeerdns
#nomppe

when disconect i get

/var/log/ppp-connect-errors is empty

/var/log/syslog

May 1 13:43:49 localhost pppd[18056]: pppd 2.4.4 started by attid, uid 0
May 1 13:43:49 localhost pppd[18056]: Using interface ppp0
May 1 13:43:49 localhost pppd[18056]: Connect: ppp0 <--> /dev/pts/2
May 1 13:43:51 localhost pptp[18061]: anon log[main:pptp.c:267]: The synchronous pptp option is NOT activated
May 1 13:43:52 localhost pptp[18066]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
May 1 13:43:52 localhost pptp[18066]: anon log[ctrlp_disp:pptp_ctrl.c:738]: Received Start Control Connection Reply
May 1 13:43:52 localhost pptp[18066]: anon log[ctrlp_disp:pptp_ctrl.c:772]: Client connection established.
May 1 13:43:53 localhost pptp[18066]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
May 1 13:43:53 localhost pptp[18066]: anon log[ctrlp_disp:pptp_ctrl.c:857]: Received Outgoing Call Reply.
May 1 13:43:53 localhost pptp[18066]: anon log[ctrlp_disp:pptp_ctrl.c:896]: Outgoing call established (call ID 0, peer's call ID 10880).
May 1 13:43:53 localhost pppd[18056]: Warning - secret file /etc/ppp/chap-secrets has world and/or group access
May 1 13:43:53 localhost pppd[18056]: CHAP authentication succeeded: Access granted
May 1 13:43:53 localhost pppd[18056]: CHAP authentication succeeded
May 1 13:43:53 localhost pppd[18056]: not replacing existing default route via 85.172.67.205
May 1 13:43:53 localhost pppd[18056]: local IP address 192.168.0.44
May 1 13:43:53 localhost pppd[18056]: remote IP address 192.168.7.201
May 1 13:44:10 localhost pptp[18066]: anon log[pptp_read_some:pptp_ctrl.c:543]: read returned zero, peer has closed
May 1 13:44:10 localhost pptp[18066]: anon log[callmgr_main:pptp_callmgr.c:255]: Closing connection (shutdown)
May 1 13:44:10 localhost pptp[18066]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
May 1 13:44:10 localhost pptp[18066]: anon log[pptp_read_some:pptp_ctrl.c:543]: read returned zero, peer has closed
May 1 13:44:10 localhost pptp[18066]: anon log[call_callback:pptp_callmgr.c:78]: Closing connection (call state)
May 1 13:44:10 localhost pppd[18056]: Modem hangup
May 1 13:44:10 localhost pppd[18056]: Connect time 0.3 minutes.
May 1 13:44:10 localhost pppd[18056]: Sent 5054 bytes, received 13318 bytes.
May 1 13:44:10 localhost pppd[18056]: Connection terminated.
May 1 13:44:10 localhost pppd[18056]: Exit.

next disconnect

May 1 13:46:47 localhost pptp[18137]: anon log[decaps_gre:pptp_gre.c:407]: buffering packet 14 (expecting 13, lost or reordered)
May 1 13:46:47 localhost pptp[18137]: anon log[decaps_gre:pptp_gre.c:407]: buffering packet 15 (expecting 13, lost or reordered)
May 1 13:46:47 localhost pptp[18142]: anon log[pptp_read_some:pptp_ctrl.c:543]: read returned zero, peer has closed
May 1 13:46:47 localhost pptp[18142]: anon log[callmgr_main:pptp_callmgr.c:255]: Closing connection (shutdown)
May 1 13:46:47 localhost pptp[18142]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
May 1 13:46:47 localhost pptp[18142]: anon log[pptp_read_some:pptp_ctrl.c:543]: read returned zero, peer has closed
May 1 13:46:47 localhost pptp[18142]: anon log[call_callback:pptp_callmgr.c:78]: Closing connection (call state)

i can reproduse it at 90%
from client i connect to sshd under vpn tunel, run mc and press Ctrl+\ (dir hot list), at 90% test pptp-client will disconnected.