Steve, I am having the exact same problem. I am able to connect the blackberry to the pc at first. The device shows up in the blackberry device manager. But I get the problem with Vista not being able to find the drivers and in the Windows Device Manager it is listed as an unknown Bluetooth Peripheral Device. I can initially connect my device to Blackberry Desktop Manager, and have tried using multiple versions of the Manager, however when it comes time to actually preform a function, I lose my connectivity and the Manager seems to freeze up.
I have spent a couple hours searching around, and will let you know if I find anything as well.