Simulating a PR2 in Gazebo fails to launch [closed]

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I'm on hydro, running on Ubuntu precise.

I am trying to simulate a PR2 in gazebo using the package pr2_gazebo. When I do the following

roslaunch pr2_gazebo pr2.launch

a bunch of stuff happens, and then it stalls, printing messages like these every 60 seconds:

[ WARN] [1434000685.721259949]: The input topic '/narrow_stereo/left/camera_info' is not yet advertised
[ WARN] [1434000685.721292292]: The input topic '/narrow_stereo/right/image_raw' is not yet advertised
[ WARN] [1434000685.721348638]: The input topic '/narrow_stereo/right/camera_info' is not yet advertised
[ WARN] [1434000685.723603227]: The input topic '/narrow_stereo/left/image_raw' is not yet advertised
[ WARN] [1434000685.723647277]: The input topic '/narrow_stereo/left/camera_info' is not yet advertised
[ WARN] [1434000685.723659035]: The input topic '/narrow_stereo/right/image_raw' is not yet advertised
[ WARN] [1434000685.723669323]: The input topic '/narrow_stereo/right/camera_info' is not yet advertised
[ WARN] [1434000685.788277445]: The input topic '/wide_stereo/left/image_raw' is not yet advertised
[ WARN] [1434000685.788486556]: The input topic '/wide_stereo/left/camera_info' is not yet advertised
[ WARN] [1434000685.788600139]: The input topic '/wide_stereo/right/image_raw' is not yet advertised
[ WARN] [1434000685.788707629]: The input topic '/wide_stereo/right/camera_info' is not yet advertised

Also, if I run the empty world version:

roslaunch pr2_gazebo pr2_empty_world.launch

it launches a gazebo window, but nothing is shown - it's just black inside the simulation window.