I have a similar problem with my Megxon Sapphire TX5500Z, a response from tech support said that it is due to the shutter sticking open for a fraction of a second longer than it should, possibly due to grit or other malfunction. This has the effect of over exposing an image and creating visable lines. Unfortuneately my problem got worse with time, and now the entire photo, no matter what scene is captured is always over exposed and severely pixelated. I am toying with the idea of opening the camera to inspect and clean the shutter, I am just not sure wether it is safe to do so.
Andrew Spies, July 2006