Gazebo: undefined symbol: _ZTIN6gazebo12CameraPluginE when creating camera plugin

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I am trying to create a camera plugin in gazebo 1.0.1. I am using Ubuntu 12.04 on VMWare (MacOS Lion).
I don't know if I did all the steps in the correct way, so let me summarize:

I installed fuerte using the official instructions. I then followed both the instructions on ROS and Gazebo webpage to create plugins. I had no problems in creating a simple helloworld plugin or a plugin to move a box.

I am referring to this tutorial about the creation of a camera.

I created a package using

roscreate-pkg camera_plugin gazebo roscpp std_msgs

then I copy-paste the suggested code in two different files put in src/ folder of my package. I edited CMakeLists.txt in order to compile the plugins:

cmake_minimum_required(VERSION 2.4.6)
include($ENV{ROS_ROOT}/core/rosbuild/rosbuild.cmake)

rosbuild_init()

set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin)
set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib)

rosbuild_add_library(CameraDump SHARED src/CameraDump.cpp)
target_link_libraries(CameraDumb ${GAZEBO_libraries})

rosbuild_add_library(CameraMove SHARED src/CameraMove.cpp)
target_link_libraries(CameraMove ${GAZEBO_libraries} CameraPlugin)`

I compiled the code using rosmake, then I edited the default empty.world (after creating a backup copy) in order to add my plugins. I copy-paste the world suggested by the tutorial, then I launched gazebo using

roslaunch gazebo_worlds empty_world.launch.

Gazebo starts but I get as error:

Error [Plugin.hh:100] Failed to load plugin /path/camera_plugin/lib/libCameraDump.so: /path/camera_plugin/lib/libCameraDump.so: undefined symbol: _ZTIN6gazebo12CameraPluginE

Any suggestion on what may be the cause of this error?