Try NOT connecting your camera to your computer.
The best way to download pictures from your camera to your computer involves removing the memory card from the camera and plugging it into a card reader (either built-in to the computer or connected via USB or FireWire). This is likely to be faster than connecting the camera to the computer, and won't run down your camera's batteries.
Once the card is plugged in, it will appear to your computer as a removable drive. You can use the operating system's drag&drop facility to copy pictures from the card to the computer's hard drive, the same way you copy any other files. Or you can use any photo cataloging program such as Picasa.
SOURCE: Transfer the photos
This can occur due to 2 reasons..
1) Bad USB port: Try connecting to a different USB port and see if it works. If it does then its probably a problem with the USB cable.
2)Bad USB cable: You can resolve this by Changing the cable or by getting a USB card reader. Specify the details of your Memory card and i will help you find a card readr that suits your card..
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