This happens to me from time to time when the computer is not connecting with the controller. I have used several laptops with my machines and have had this problem many times. On one machine I have a dedicated Dell Latitude. This machine seems to have tighter USB ports than the other laptops I have/had. It was refurbished machine when I bought it and I keeping checking with my computer guy for another. My computer guy thinks that it is probably different USB port manufacturers.