EVAL232R FTDI, Future Technology Devices International Ltd | 768-1023-ND | DigiKey
is the one that Adam uses and could be counted upon to work.
I only use USB to serial adapters that contain the FTDI chip set.
I use one that is similar looking to the one in Paul's video in the post above this one.
It has a blue molded connector on a USB cable. It cost $9.95 on Amazon as I recall.
I probably have 3 different USB to serial adapters and they all work with RTD explorer.
I can see where you would be concerned about which one to use since you had so much trouble!