There are many posts about this issue in the Whistler, RadioShack and GRE scanner forums.
Many people don't understand that there is a separate piece of software, called a driver, that exists between the application and the cable that supports communication between the two. Windows does a very poor job of installing the correct driver for many devices (the so-called "plug and play" function of Windows). The driver is NOT included with the programming application. The user must locate and install the correct driver for the cable being used and that is compatible with the particular version of Windows being used. For most GRE/RadioShack/Whistler cables, the FTDI drivers seem to work pretty reliably. For 3rd party cables, it's anyone's guess.
Search the forums listed above for more details on locating and installing the driver. Note: the driver for the cable that programs PRO-106 "family" of scanners is NOT the same as the driver required to establish communication with the SD-card scanners - PSR-800, WS-1080, TRX1, TRX2, etc.