Treatment period #1 (Visits 2 - 5; day 0 - 28): Baseline measures will be recorded and subjects randomized to treatment order at visit 2 (day 0). Study medication as well as rescue medication (l-dopa, a non-blinded active treatment to be used within a limited dose range as described in the detailed protocol) will be dispensed. Subjects will begin treatment period #1 immediately after this. The study medication will be titrated within the allowed range according to subject's reported symptoms during visit 3 (day 7), visit 4 (day 14), telephone contact (day 21). Visit 5 will occur on day 28 and will include assessment of outcome measures for the first treatment period. Visit 5 will also mark the beginning of the second treatment period.