|USB devices may not work correctly when they're connected to certain USB ports e.g. ports in a hub or on the front of a desktop case. If you have a desktop computer, you may have an IRQ sharing problem you need to fix, or your power supply may be starting to fail. |
See response 3 in this:
Also - if you are using a USB extension cable, some of them have inadequate wiring and will not work properly with some USB devices.