Openni2 problem with 2 xtion cameras

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Hello everybody

I'm wanting to activate 2 xtion cameras with openni2 using ROS. One of the cameras works well and it shows the image (I do it checking with rqt), however, the other one is always showing a message telling:

Warning: USB events thread - failed to set priority. This might cause loss of data...
[ INFO] [1452532881.196199692]: No matching device found.... waiting for devices. Reason:

openni2_wrapper::OpenNI2Device::OpenNI2Device(const string&) @ /tmp/buildd/ros-indigo-openni2-camera-0.2.5-0trusty-20151111-0829/src/openni2_device.cpp @ 74 : Device open failed
    Could not open "1d27/0601@2/3": USB transfer timeout!

...And of course in rqt it doesn't show anything.

Is there any limitation about using these 2 cameras at the same time? Do you have any clues about why this thing happened?

Thanks.