[ros-users] exception in transform listener

Hi all,

I'm trying to follow the tutorial on transform listener:

http://www.ros.org/wiki/tf/Tutorials/Writing%20a%20tf%20listener%20(C%2B%2B)

I'm trying to use it with simulated pr2 and gmapping to determine location
of the robot relative to the map. What I'm getting is following message:

[ERROR] 4546.007000467: Could not find a connection between '/map' and
'/base_footprint' because they are not part of the same tree.Tf has two or
more unconnected trees. When trying to transform between /map and
/base_footprint.

although, rviz shows the transforms and connections just fine, tf_echo
outputs the transforms as well and tf_view prints out just one tree
(attached).

Any hints on what might be the problem would be very appreciated.

Michal