Unexpected navigation tf warning

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Sometimes, while launching the autonomous navigation the following warning occurs :

[ WARN] [1372337372.793829100]: Waiting on transform from /base_footprint to /map to becomeavailable before running costmap, tf error:

and after that, I can't manage to get the navigation to work again. Most of the times, it does work fine. I don't understand why sometimes it doesn't.

The manipulations I do is launching turtlebot_bringup minimal.launch and then launching the navigation's nodes thanks this launch file :

<launch>
  <include file = "$(find turtlebot_bringup)/launch/3dsensor.lau
nch">
    <arg name = "depth_processing" value = "false" />
  </include>
  <!--Map server-->
  <node name = "map_server" pkg = "map_server" type = "map_serve
r" args = "/maps/my_map.yaml"/>
  <include file = "$(find turtlebot_navigation)/launch/includes/
_amcl.launch">
    <arg name = "initial_pose_x" value = "16.6"/>
    <arg name = "initial_pose_y" value = "34.55"/>
    <arg name = "initial_pose_a" value = "1.59"/>
  </include>
  <include file = "$(find turtlebot_navigation)/launch/includes/
_move_base.launch"/>

I first thought it was because the nodes which update tf tree needed time to initialize... But I am not sure that is the reason.