Polhemus Liberty Latus error

[VIZUNN]

Hi

I launch a marker with the PiMgr program supplied with the Liberty Latus. The marker is launched successfully and tracks accurately when run with PiMgr. When I run Vizard with the following code, while the PiMgr is still open, I get some errors.
code:
pol = None
pol = viz.add('polhemus.dle')

if not pol.valid():
viz.message('Failed to initialize Liberty Latus')
else:
sensor1 = pol.addLibertyLatus(marker=3, receptor=3)
viz.link(sensor1,bone1,mask=viz.LINK_ORI)

errors:
** ERROR: Failed to connect to a Patriot Wireless/Libert LATUS: Device not found
** ERROR: Failed to create extension sensor with polhemus.dle
** ERROR: Link failed (source linkable is invalid)

If I close PiMgr and run the same code, the system hangs and says:
winviz.exe has encountered a problem and needs to close. We are sorry for the inconvenience.

The marker number is correct and I have tried the addLibertyLatus() method without parameters and I have also re-installed the Polhemus drivers and software without luck.

Any help will be much appreciated.