problem with nxt_lejos_lcp_proxy

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Hi everybody! I'm a researcher, I'm working with ROSJava and a NXT. I'm trying to run LCPProxy.java but I have a problem. After launching the node I get this output:

* Configurate ROS Node

*********************
* Running LCPProxy *
*********************

ROS Node Path: /home/camilla/my_workspace/nxt_lejos/nxt_lejos_lcp_proxy/
* Reading property file
Path: /home/camilla/my_workspace/nxt_lejos/nxt_lejos_lcp_proxy/nxt_lejos_ros/lcp_proxy.properties
BRICK-NAME: OKAY
CONNECTION: USB
YAML: NXT.yaml
Differential navigation features enabled
WHEEL_DIAMETER: 5.6
TRACK_WIDTH: 16.0
REVERSE: true
* Connecting with a NXT brick
Log.listener: Protocols = 1
Log.listener: Search Param = null
Log.listener: Searching for any NXT using USB
Found NXT: Unknown 001653079D95
ROS Node connected with a NXT brick
* Bind NXT brick with ROS
* Processing YAML file
YAML Path: /home/camilla/my_workspace/nxt_lejos/nxt_lejos_lcp_proxy/NXT.yaml
list size2
Type is ultrasonic
I found an ultrasonic  sensor description
ultrasonic_sensor
PORT_1
10.0
point1
Found NXT: Unknown 001653079D95
Failed to open connection to the NXT

It seems that the configurate and the connect steps succeed, but there is a problem in the bind() one. In particular in during the first iteration of the for loop in processYAML(). Infact debbuging the code I saw that the last instruction called is:

us = new UltrasonicSensor(node, port);

But I can't figure out why and where there is a new attempt to connect to the brick which produces the last two lines of the output:

Found NXT: Unknown 001653079D95
Failed to open connection to the NXT

can you help me find a solution?or at least to understand where in the code and why there is the new attempt of connection?

I'm using a NXT with the traditional Lego firmware and a usb connection.

my YAML file is:

nxt_robot:
  - type: ultrasonic
    name: ultrasonic_sensor
    port: PORT_1
    min_range: 0.01
    max_range: 2.5
    desired_frequency: 10.0
  - type: differential_navigation_system
    name: pilot
    port: PORT_AC
    desired_frequency: 10.0
    track_width: 16.0
    wheel_diameter: 5.6
    reverse: true

(specifing another sensor or actuator as first element of the yaml file I get the same error, so the problem isn't specific of the ultrasonic sensor).

my lcp_proxy.properties file is:

NXT-BRICK: OKAY
CONNECTION-TYPE: USB
YAML-ROBOT-DESCRIPTOR: NXT.yaml
DIFFERENTIAL_NAVIGATION_FEATURES: true
WHEEL_DIAMETER: 5.6
TRACK_WIDTH: 16.0
REVERSE: true

Looking forward to hearing from you. :)