Hi,
That error ("MainWindow.cpp:2740::processRtabmapEvent3DMap() Map received with code error 1!") happens when rtabmap node is dead or is not in the same namespace than rtabmapviz (i.e., rtabmapviz cannot communicate with rtabmap node). Look at the terminal for any errors.
I tested with 0.11:
$ roslaunch rtabmap_ros demo_two_kinects.launch
I tested 0.10 (actual ros binaries) and it works but odometry is less good.
cheers