I have windows 7 x64. This is what I had to do. Download and install the wmdc for x64:
http://www.microsoft.com/downloads/d...displaylang=en
Start the install without your phone connected to the usb. You see the install get to a point where it looks like it either quit or is no longer doing anything. At this point connect your phone and it will finish the installation. After doing this I can now sync and flash my phone.