I'm on my second GRC-61 cutter and it's hooked up usb.
First one was struck by lightening.
Mine is hooked up to xp with a serial to usb converter cable that
I got from signwarehouse.
It has worked fine for about eight years with no problems.
I'm also using LXI 6.6 v1 software with usb dongle.
I did have to download a usb hasp driver, so the
computer would see the dongle.
You might ask signwarehouse about the serial-usb converter cable.
Works fine for me.