I opened up my RT systems cable and found that it has a FTDI chip in it.  It's a standard chip, but they programmed it with their own USB vendor ID codes so that it loads their custom driver.  I doubt they did this to be mean spirited, but who knows for sure.  This gives them the ability to make their software works in a plug-and-play fashion where you don't need to configure any port settings.  Just plug in the USB cable and it will automatically find your radio.

However, because it's a standard chip, I was able to get their cable to work by downloading the regular FTDI Virtual Serial Port (VSP) driver and forcing it to be used instead of the default one.

Here's what worked:

- Download the VCP driver zip file and expand it to a folder - http://www.ftdichip.com/FTDrivers.htm

- Open up the device manager and update the driver for the RT cable device

- Go though the "let me choose" and "have disk" options to point it at the folder where the files were unzipped.

- Install the driver that shows up even if it warns about it not being compatible.

- The device now shows up as "USB Serial Converter", go to its properties/advanced tab and check the box called "Load VCP".

- Unplug the device and plug it back in

- A new com port device will show up, but a driver will not load for it automatically.

- Go thought the same process as before to install the driver from that unzipped folder.