The most likely cause is that the USB Controller on your system turns off automatically after a certain period of inactivity. If you are using Windows XP, follow the instructions below to disable power save option for the USB Controller on your computer:
- Open the Windows Control Panel and double click on the System.
- Click on the Hardware tab and then press the Device Manager button.
- Double click on the Universal Serial Bus Controllers.
- Right click on the USB Root Hub.
- Go to Power Management tab and uncheck the “Allow the computer to turn off this device to save power”.
- If the above procedure doesn’t resolve this issue, try connecting the reader through a self-powered USB hub