Hi everyone,

My name is Grace Lee and I am an undergraduate research assistant at USC's  
Interaction Lab. I am currently writing a urdf for a human model that will  
be interacting with PR2 in the gazebo. When I run the command "roslaunch"  
on my launch file, I get this error: [ERROR] 1277225053.038870000: Could  
not compute link poses. The tree or the state is invalid.

I have parsed the urdf and the tree structure seems correct - ie $ rosrun  
urdf check_urdf [my_urdf_name].xml shows that there is one child (which is  
correct btw). The urdf and the state_publisher.cpp seems to be correct as  
well. Any insights into the source of this problem would be greatly  
appreciated.

Sincerely,

Grace Lee