Cannot take a picture--message: "your card is

You're right in saying that if you get ANY onscreen message with the computer connected, the LCD and its driver circuits are likely OK. I don't have that exact cybershot, but I have had a few, and most have a menu item to turn off various screen content, including the entire display. Its likely a battery saving feature, but if you turn it on and hit the MENU button and still see nothing, there must be some actual defect. If all else fails, before contacting SONY, take the battery out and wait at least 5 minutes and then replace.

Because the same message appears when you insert the card into other cameras the most likely problems are that the card is full or defective.
Have you tried another card in your camera? If not then you should do so. If it works then it confirms your other card is full or defective.

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). 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 management program such as Picasa.
Organize edit and share your photos

Format the memory card in the camera, not the computer. Also, it could be a memory card issue, do other cards cause the camera to return the same message. If yes, then it well could be the camera.

SD and SDHC cards have a slide switch along one edge. The position farthest from the contacts locks the card, protecting it from writes. The position nearest the contacts unlocks the card.

its a hardware fault like mmc ic

The words "Digital Noise Filter Off" and "digital Noise Filter On" appear on the top left and right and side of the screen and the words " Auto Visulisation" appear on the bottom of the screen all the time when watching normal T.V.(series 5 lcd) and if we make changes regarding in setting in picture option in mode.then after 20-30 min againg it displays same message

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 any photo cataloging program.

Sounds as if the memory card may be corrupted. In order to remove the write protect, make sure you have downloaded and saved all of the images from the memory card to your computer and then having the card in the camera you will need to run the format option and this will permanently remove the write protect as well as all of the images from the card.
The card should be able to be used again after the write protect is removed.

You need to format the card before you can use it. Pick "Format" from the camera's menu to initialize the card.