I'm going to take a stab at this. I don't know if I'm right, but I'm going to guess you have a hardware problem, possibly a faultering connection inside your camera somewhere.
I suspect this because I have IR modified a number of Nikon Coolpix cameras and once when I put one together I got some similar distortion. I took it apart and found that the ribbon cable that connects the CCD board to another circuit board wasn't in the whole way.
CCD chips are analog devices (they output voltages, not bits), so if a connection isn't in solid, it can cause distortion in the voltages and electrical signals which are misread by the analog digital converter and can show up as distortion in the images.
I'm somewhat experienced taking electronics apart and putting them back together. I took an A70 apart before and it was the biggest pain in the world, VERY difficult, so I don't recommend it at all. I also got thrown down on the floor in pain when the flash's capacitor (which I knew to avoid) gave me one hell of a shock.
I don't suspect this is anything you can do much about.
That's just my speculation based on experience. Good luck.
~Bill