this solves the problem

I had a similar problem but finally got it to work, the pc850 works
with a newer version of the widcomm bluetooth driver. (don't bother
using windows built in bluetooth control panel, it will not work, i
don't even think any hardware actually works with it unless it is
shipped with your computer)

I got this version to work with windows vista and my pc850

http://rapidshare.com/files/7270107/...0_x64.rar.html

This is a newer version of the drivers that were included with your
pc850 and what motrorola offers themselves on their support page.
It worked like a charm, and my pc no longer freezes anymore whenever i
plug in my dongle.

There is an even newer version, but i have yet to try it out, frankly
since the 5.1.0.2700 works i'm not going to push my luck and try the
newer version but in case you want it, its available here:

http://rapidshare.com/files/47514859...32bit.rar.html

Let me know how it goes for you, just trying to spread the information
because motorola is not really being helpful with vista
implementation, and
they are not telling their customers that there are newer versions of
the widcomm drivers
available online, you just have to scour the internet for them.

-favian