Error thrown from publisher.h header file

edit

We're trying to communicate via publisher/subscriber nodes between a laptop and a PC-104, but whenever we try to send a message, this error is returned:

QMetaObject::connectSlotsByName: No matching signal for on_button_move_to_clicked(int) file = /opt/ros/fuerte/include/ros/publisher.h line = 102 cond = false message = Trace/breakpoint trap

Which is generated by this line in publisher.h:

  if (!impl_)
     {
       ROS_ASSERT_MSG(false, "Call to publish() on an invalid Publisher");
       return;
     }

But we're not sure what "!impl_" means, so we can't figure out what exactly is triggering this error. Has anyone dealt with this before?

http://mirror.umd.edu/roswiki/doc/api/roscpp/html/publisher_8h_source.html (Full text of publisher.h)