I've got a Dell Optiplex 3020, running 64 bit Win 7 Pro (one of 3 identical machines), that has had this problem on & off for a while. I've got a USB 3.0 external HD connected to computer for backing up (Acronis True Image), that from time to time the 'USB device not recognized' message would pop up, causing my backups to not work. I called Dell, who had me DL a driver update, that seemed to fix for a short while. I had this question posted in Dell's forum & another user suggested using a Y-cable, saying it would draw more power & fix my problem. I tried this & it also appeared to work for a while, but once again, the problem is back. Would an add-in card or a powered USB hub work any better?
Any advice appreciated!