I have had really bad results using any USB to RS232 converters. I have tried a number of different dvices with the same bad results. Most of these use a chip called PL2303. I've had trouble with the character timing on this chip, sometimes it waits too long between sending characters and the receiver times out.
That said, I've never used it on my Hurco because I have an old laptop that has a hardware serial port I use to archive programs and drip feed to the Hurco.