Vista - Bluetooth v1.2 Dongle + Plantronics Voyager 510

ok, once more a bluetooth problem with vista build 5728.

when i plug in the bt usb dongle, it is found and installed
properly. in the device mangager i can see a plantronics usb
bluetooth device, but marked with an asterisk. the details say
it is a generic usb driver, but the device would not work.

then after a little googling i found out that i should try using
the (patched) widcomm bt stack. installed it, and pointed the
plantronics device to use one of the widcomm stack drivers (in /bin
directory) which let me choose between bt audio and bt high quality
audio drivers. i tried both paths, and the plantronics device was
no longer wearing the asterisk.

i was then able to choose "high quality audio (plantronics usb)"
in skype, and tried called the test caller. While the plantronics device
makes the proper click sound (connected), i cant either hear the
caller nor speak to it.

any further ideas?

Regards, Sascha