Once more THREE minutes VPN connection

Hello!
I have problem with vpn connection. There are two vpn clients. One of
them have a stable connection and the second have only three minutes
connection. They use win xp sp2 system. They use two diffrent ISP.
I turned on debuggin and loggin on RAS and:
(connection: 19.30, tree minutes idle, 19.33 self disconnecting)
auto - disconnecting is off on server (idle time)
First disapper VPN client in MMC RAS Console, connection is lost, after 15
sec. on task bar laptop disapper connection without any error...

PPP.LOG
[3764] 10-28 19:30:33:759: Line up event occurred on port 134
< ..............>
[3764] 10-28 19:30:35:571: AuthAttribute SessionTimeout = 0
[3648] 10-28 19:33:40:758: PPPEMSG_LineDown recvd, hPort=134
<...............>

RASAUTH.LOG
[1232] 19:30:34:337: RasAuthProviderAuthenticateUser called
<...............>
[1232] 19:30:35:571: IASResponse = 4, FailureReason = 0x0
[5544] 19:33:42:757: RasStopAccounting called

RASMAN.LOG
[3648] 10-28 19:30:33:634: WorkerThread: Async work event signaled on
port: VPN4-127
<................>
[3648] 10-28 19:33:40:758: WorkerThread: Disconnect event signaled on
port: VPN4-127
[3648] 10-28 19:33:40:758: OVEVT_DEV_STATECHANGE. pOverlapped =
0x2a62b90
[3648] 10-28 19:33:40:758:
d:\srvrtm\net\rras\ras\rasman\rasman\worker.c, 1995: Disconnecting port
134, connection 0x0, reason 1
[3648] 10-28 19:33:40:758: Disconnecting Port 0xVPN4-127, reason 1

IGMPv2.LOG
[1108] 19:30:29: Entering _WT_ProcessTimerEvent()
<...................>
[1232] 19:32:40: In _DebugCheckLowTimer
[1216] 19:33:42: Entering DisconnectRasClient for IfIndex(10002),
NextHop(10.10.10.248)
[5544] 19:33:42: Entering WF_ProcessProxyAlert()

TAPI23.LOG
[3736] 19:30:33:634: [INFO ] AsyncEventsThread: msg=23, hDev=x103db,
p1=x0, p2=x10242, p3=x4
<........................>
[3736] 19:33:40:758: [INFO ] AsyncEventsThread: msg=2, hDev=x10242,
p1=x4000, p2=x0, p3=x0
[3736] 19:33:40:758: [INFO ] AsyncEventsThread: posting msg,
hwnd=x100e4
[3672] 19:33:40:758: [TRACE] TAPIWndProc: received WM_ASYNCEVENT,
hwnd=x000100E4
[3672] 19:33:40:758: [INFO ] Calling app's callback, hDev=x10242,
Msg=2, dwInst=x1477a8 P1=x4000, P2=x0 P3=x0

ROUTER.LOG
[1232] 10-28 19:30:32:180: RouterIdentityObjectOpen returned 0
<.........>
[1216] 10-28 19:33:40:758: Rasman state change received from port 134,
2->4
[1216] 10-28 19:33:40:758: SvDevDisconnected:Entered, hPort=134

KMDDSP.LOG
[3720] 19:30:33:634: ! AsyncEventsThread: got a line event
<.........>
[3720] 19:33:40:758: ! AsyncEventsThread: got a line event
[3720] 19:33:40:758: ! ProcessEvent: event(000A87C8), msg(2),
ht_line(00BC0000), ht_call(8000009B), p1(00004000), p2(00000000),
p3(00000100)
[3720] 19:33:40:758: ! PE::fnLineEvent(CALLSTATE): htline(0001001E),
htcall(00010052), p1(00004000), p2(00000000), p3(00000100)
[3720] 19:33:40:758: ! PE::fnLineEvent(CALLSTATE_IDLE):
htline(0001001E), htcall(00010052), p3(00000100)
[1936] 19:33:40:758: lineGetCallStatus(66): call(00C00006)
[1936] 19:33:40:758: ! SyncDriverRequest: oid(GetCallStatus), devID(1),
reqID(367), hdCall(000071E8)
[3628] 19:33:40:758: lineDrop(93): reqID(101a8), call(00C00006)
[3628] 19:33:40:758: ! AsyncDriverRequest: oid(Drop), devID(1),
ReqID(101a8), reqID(368), hdCall(71e8)