usb 6501 and pyvisa

Hi

I'm trying to control the I/O of the USB 6501 device from NI via pyvisa. I can launch the test part from NI max and it works well. However when I want to see the device with ResourceManager() with pyvisa,I can see all my devices in the list except this one.

Does someone has a clue for this problem ?

Configuration : Windows 7, Spyder (Python 2.7), NI-DAQmx 9.9.0f0.

Thanks