Did you check the Mach3 website and the Warp9 website for this?
I am not sure where you got your drivers but this is worth reading through.
It says something about not using the drivers on the FTDI site, to use these.
Its been almost 3 years sense I installed my SS, and even then it was only bench tested so I cant help you much here. Looks like i have a lot to go through when I fire my machine up myself.