digicam problem with lines in image

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I have a Sony DSC-F505V and have taken over 3000 pictures with it. A few
days ago I took 20 pictures on a snowy day in Yosemite. The next morning I
turned on the camera to take a glorious picture of Yosemite Falls and
noticed horizontal lines that moved around that were superimposed on an
image. I changed the battery and memory stick but the lines are still there.
The previous day's photos look fine still. Even when the camera is plugged
into an outlet without the battery, the images still have those lines
whether the camera is in "still" or "movie" mode. Could a melted snowflake
have shorted out some component? What can I do to fix this problem? --Louann