This study will determine the highest amount of idebenone that can be taken without harmful side effects in children, teenagers, and adults with Friedreich's ataxia, a progressive degenerative disease that affects several body systems. Studies in France and Canada showed that patients with Friedreich's ataxia who took idebenone had a decrease in the size of their left ventricle (main pumping chamber of the heart), which is often enlarged in this disease. It is possible that idebenone may also prevent the progression of nervous system degeneration in Friedreich's ataxia.