RTL-SDR Error code -3

Hello all I am trying to get the python wrapper "pyrtlsdr" working on Windows, it works fine on Linux The dongle works fine in SDR-SHARP.exe It imports correctly but prints the following error when I try to initialize the Dongle: Traceback (most recent call last): File "C:\Users\M0ZJO\Desktop\RA_Astro\FFTPrint Test.py", line 4, in <module> sdr = RtlSdr() File "build\bdist.win32\egg\rtlsdr\rtlsdr.py", line 60, in __init__ % (result, device_index)) IOError: Error code -3 when opening SDR (device index = 0) RTL_FM also returns the same error. Can anyone help? I would be very grateful! Many thanks Jonathan/M0ZJO