This study will compare the efficacy and the safety of ABT-894 (1mg, 2mg or 4mg capsules) administered BID to placebo in the treatment of DNP. Another treatment arm will be Duloxetine 60mg administered once daily (QD). Approximately 275 subjects will be enrolled into the study at approximately 50 sites in both the United States and Europe. The study will be divided into the following periods: Screening/Washout (21 days) followed by a Baseline Visit, an 8-week Treatment Period and a 1-week Follow-up Visit.