Vivitar 8400 suddenly show white horizontal lines ! is it reparable as camera hardly used since new

Vivitar lists no firmware updates for the 8400. See http://www.vivitar.com/products/1/digital-cameras/17/vivicam-8400

You can download the manual and request the Vivitar Experience software from the manufacturer's web site at
http://www.vivitar.com/products/1/digital-cameras/17/vivicam-8400

You might want to consider 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 iPhoto or any other other photo cataloging program.

You can't. The 8400 was designed as a camera, storing images (and videos) to a memory card. It was not designed to stream videos live to another device.

This is more than likely a Manufacturing problem. A lot of Vivitar cameras have this problem as well as many others that are usually not the consumers fault. Just a glitch in the technology. I alone have gone through four Vivitar cameras in the last six months. The best thing to do is contact Vivitar directly. This is there website: www.vivitar.com It is best to see if you can find the number for technical support. To see if they can give you a refund or replace it for you. I hope this helps. -Richard

Use a card reader instead of your camera.

http://vivitar.com/products#Digital Cameras/24/17/Support

Your shutter speed may be set too low. Try using the "auto" setting on your camera.

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.

in what mode do you take the pictures?

have you tried to reset it ?

yes.