I got the USB CAT cable to install successfully in Windows 8.1.
Access the following website and then download the zip folder from the “USB-Serial Driver” link.
Unzip the folder, extract the files, and then install the PL-2303 exe file. This is a Windows 7 X64 file but it works in Windows 8.1.
Once installed, connect the USB-USB CAT cable to your PC and to your LD-5. Enter the Device Manager and you will (likely) see the offending Yellow warning icon imposed on the Prolific driver/icon. Right click the icon. Access Properties. Choose Driver Tab then Click Update Driver. Choose the Browse option then choose the “Let me pick . . .” option. Be sure to select the version no. 18.104.22.168. It should work and you should now be able to update the LD-5 firmware.
Be aware of a couple of things! First, if you get out of the update program, etc. and then start it all over again, you may have to re-choose 22.214.171.124. I know I had to do this. Second, it is my understanding that when Windows does its periodic updates, it will re-install the latest Windows 8.1 version of the Prolific drivers. Currently this is 126.96.36.1995. You will have to roll-back or re-choose the 188.8.131.52 again. Yes, I know. A PITA . . . but what else is there to do?
Note to the LNR folks: I strongly suggest the next time you update the LD-5 that you provide a USB CAT cable with another chipset such as FTDI. Just saying . . . .
Good luck everybody!