Occasionally you may see vertical lines in your videos. These are caused by sun flare and are not uncommon to CMOS sensors like the ones used in most consumer digital cameras such as Contour's.
If the sunlight hits the camera just right, it will overload a digital camera’s sensor and result in the vertical lines seen in your videos. This generally occurs when the sun is positioned slightly above the camera's field of view. However, if moving away from the sun or with the sun not just above the camera, this problem shouldn’t occur.
To minimize this effect, you can try using a polarized filter. These filters can be purchased from most camera shops.