Cannot connect to checkpoint vpn: "Maximum retries exceeded for tunnel. Closing."

Hi
it seems that something is going wrong when I try to connect to a checkpoint firewall from my Ubuntu 11.04 laptop.

Here the connection failure log:

ipsec_setup: Starting Openswan IPsec U2.6.28/K2.6.38-11-generic...
Sep 1 10:41:24 ba ipsec__plutorun: Starting Pluto subsystem...
Sep 1 10:41:24 ba ipsec__plutorun: adjusting ipsec.d to /etc/ipsec.d
recvref[22]: Protocol not available
xl2tpd[11486]: This binary does not support kernel L2TP.
Starting xl2tpd: xl2tpd.
xl2tpd[11489]: xl2tpd version xl2tpd-1.2.6 started on ba PID:11489
xl2tpd[11489]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc.
xl2tpd[11489]: Forked by Scott Balmos and David Stipp, (C) 2001
xl2tpd[11489]: Inherited by Jeff McAdams, (C) 2002
xl2tpd[11489]: Forked again by Xelerance (www.xelerance.com) (C) 2006
xl2tpd[11489]: Listening on IP address 0.0.0.0, port 1701
Sep 1 10:41:24 ba ipsec__plutorun: 002 added connection description "WORK"
003 NAT-Traversal: Trying new style NAT-T
003 NAT-Traversal: ESPINUDP(1) setup failed for new style NAT-T family IPv4 (errno=19)
003 NAT-Traversal: Trying old style NAT-T
104 "WORK" #1: STATE_MAIN_I1: initiate
003 "WORK" #1: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-02_n] method set to=106
106 "WORK" #1: STATE_MAIN_I2: sent MI2, expecting MR2
003 "WORK" #1: NAT-Traversal: Result using draft-ietf-ipsec-nat-t-ike-02/03: i am NATed
108 "WORK" #1: STATE_MAIN_I3: sent MI3, expecting MR3
004 "WORK" #1: STATE_MAIN_I4: ISAKMP SA established {auth=OAKLEY_PRESHARED_KEY cipher=oakley_3des_cbc_192 prf=oakley_sha group=modp1024}
117 "WORK" #2: STATE_QUICK_I1: initiate
003 "WORK" #2: ignoring informational payload, type IPSEC_RESPONDER_LIFETIME msgid=107fc743
004 "WORK" #2: STATE_QUICK_I2: sent QI2, IPsec SA established transport mode {ESP=>0x2123226d <0x4ab10bb1 xfrm=3DES_0-HMAC_SHA1 NATOA=none NATD=none DPD=none}
xl2tpd[11489]: Connecting to host xxx.xxx.xxx.xxx, port 1701
xl2tpd[11489]: Maximum retries exceeded for tunnel 8540. Closing.

Here the ipsec.conf generated by L2TP IPsec VPN Manager:

# /etc/ipsec.conf - Openswan IPsec configuration file
# $Id$

# Manual: ipsec.conf(5)

# Created: Thu Sep 1 09:57:10 2011
# by: The L2TP IPsec VPN Manager application version 1.0.0
#
# WARNING! All changes made in this file will be lost!

version 2.0 # conforms to second version of ipsec.conf specification

config setup
 # plutodebug="parsing emitting control private"
 plutodebug=none
 strictcrlpolicy=no
 nat_traversal=yes
 interfaces=%defaultroute
 oe=off
 # which IPsec stack to use. netkey,klips,mast,auto or none
 protostack=netkey

conn %default
 keyingtries=3
 pfs=no
 rekey=yes
 type=transport
 left=%defaultroute
 leftprotoport=17/1701
 rightprotoport=17/1701

# Add connections here.

conn WORK
   authby=secret

 right=xxx.xxx.xxx.xxx
 rightid=""
 auto=add

Here the xl2tpd.conf file:

; /etc/xl2tpd/xl2tpd.conf - configuration file for use with L2TP over IPsec.
; $Id$

; Manual: xl2tpd.conf(5)

; Created: Thu Sep 1 09:57:10 2011
; by: The L2TP IPsec VPN Manager application version 1.0.0
;
; WARNING! All changes made in this file will be lost!

[global]
; listen-addr = 192.168.178.28
debug avp = no
debug network = no
debug packet = no
debug state = no
debug tunnel = no

[lac WORK]
lns = xxx.xxx.xxx.xxx
pppoptfile = /etc/ppp/WORK.options.xl2tpd
length bit = no
redial = no

Can someone help me to solve the problem?
Thanks
Paolo