No navigation device found

Hi,

I have a Sony Gps device, NV-U71T, and I need to update the firmware in the
device.

I have installed Windows Mobile Device Center 6.1, but when I connect the
GPS and try to update the firmware I get this message "No navigation device
found". I don't know what is the problem and when I connect the device I get
the "sound" telling me that Windows Vista has reacted somehow on the
connection.

This is very important for me and if you can help, your help will be greatly
appreciated.

Nb. I have tried to uninstall the Windows Mobile Device Center 6.1 and
install it again, but the result is the same.

--Gudmund