This is a 28-week extension to a study of the safety and effectiveness of three doses of vildagliptin, an unapproved drug, compared to placebo in lowering overall blood glucose levels in people with type 2 diabetes who have not been previously treated with drug therapy to lower their blood sugar. The purpose of the extension study is to gather long-term safety and efficacy data for vildagliptin in people with type 2 diabetes.