I'm not sure which plugin you downloaded, but the only VRPN plugin you should be using is the one that comes with Vizard installer.
Regarding the data being incorrect, can you be more specific? The VRPN plugin should return the raw values it receives from VRPN. Are you getting any timeout error messages in the output window?
Also, for 6DOF tracking data you can use the following sensor methods to access the data, instead of using the raw linear array:
Code:
sensor = vrpn.addTracker(...)
pos = sensor.getPosition()
quat = sensor.getQuat()
euler = sensor.getEuler()
axisAngle = sensor.getAxisAngle()
matrix = sensor.getMatrix()