Comparison of ISO 100 vs 1600 on the Panasonic Lumix GH1, to demonstrate the vertical lines observed on my camera. The ISO 100 shot is first, with the 1600 shot starting at 1:15.
Both shot with the stock lens.
In the ISO 1600 shot, notice the difference between the vertical lines and regular noise that is expected at high ISO's. The lines stay in the same position, very similar to scratches on traditional film. This is especially apparent at 1:28 when the ice cube slides out of focus.