Description
You may be receiving this error when you are trying to use more then one USB-Blaster™ Rev. C programming cable. Rev. C programming cables were not given unique serial numbers as Rev B or the original USB-Blasters so on some operating systems this will cause a USB conflict.
Resolution
To use multiple USB-Blasters it may be possible to use a USB hub. With the USB hub, you can plug the USB hub into one of the USB ports on your computer then plug both USB-Blaster Rev. C cables into the hub and this should enable you to use both USB-Blasters. When using a USB hub it is recommended to use a powered USB hub.
Another work-around would be if you have USB-Blaster Rev. B or Rev. A programming cables then you can have one Rev. C and another Rev. plugged into the computer at the same time without the use of a USB hub.