Nikon has filed a patent infringement suit with the Tokyo District Court against Japan's Sigma Corporation. The lawsuit 'seeks an injunction against Sigma's manufacture and sale of infringing interchangeable lenses with vibration reduction for single lens reflex cameras, along with damages for past infringement.' Nikon do say they tried to resolve the alleged infringement through negotiations but an agreement could not be reached.
Nikon say: "Nikon has invested considerable resources in the form of research and development over a period of many years. Such investments have created intellectual property that are important business assets of Nikon and have enabled Nikon to continuously provide the products and services that satisfy its customers requirements."
We are currently waiting for a response from Sigma. We shall update the story when we get more details through.