Hi some lights do cause an scalettature , a pixel effect on items , why this is happening and how to avoid?

here an image of what I mean , any solution?

http://img138.imageshack.us/img138/7378/throneroom3.jpg

Visual "Striping" artifacts sometimes occur when using shadow lights, as seen in Fig 8.2a. This can be fixed by manually adjusting the Depth Bias of the light casting the shadows. Hold "alt+B" while dragging the mouse. Adjust the light only as much as required to get rid of the striping, as going too far can cause another visual error which can make shadows appear to float.

From Bethesda lights and FX Tutorial

thankyou this fixed it ....