I too only use a FTDI USB / serial cable with my HT. I use this cable with my Yaesu VX-6 on three separate computers. One workstation and two field laptops. My FTDI cable connects 100% of the time with fail proof HT uploads and downloads. 

As I read all of the gross Prolific connection failure support requests, I am now wondering why Hams even waste their time in dealing with using Prolific USB / serial cables?

"An idea is not responsible for the people who believe in it."