About two years ago there was a rash of bad CCD's that made their way into consumer imaging products from several different brands, Sony included (they are actually the company that manufactured the faulty sensors).
For Sony products, you've got until October of this year to have your camera repaired free of charge - Sony even pays for the shipping.
Other companies have different repair policies related to this issue.
Look
here to see if your camera is on the list, and instructions on getting it fixed.