This sounds to me as though something is interfering with the connection between Phoenix and and your phone. First off check the most obvious things like ensuring that you have a good solid cable connection and that it's plugged into a verifiably working USB port.
The other thing that might be causing issues is if your PC Suite/Nokia Cable Driver didn't uninstall fully. If this is the case try the method I used and install Phoenix and Diego on a Virtual Machine. I used VMWare server (http://www.vmware.com/products/server/
) which is nice and easy to get to grips with. Only thing to remeber here is that you give the Virtual machine access to the hosts USB ports in the Virtual machine settings. This method has the advantage that you can guarrentee you are running on a clean installation of Windows without having to format your existing PC.