 SB497115 is an oral agent which activates the thrombopoietin receptor and increases platelet counts in healthy volunteers. This study is examining several different doses of SB497115 as a treatment for patients with chronic hepatitis C-related thrombocytopenia who are potential candidates for antiviral treatment with pegylated interferon and ribavirin. The study will be conducted in two phases, Parts 1 and 2. In Part 1, study subjects will be randomized to 4 weeks of SB-497115-GR or placebo administered daily without antiviral therapy. Subjects who successfully complete Part 1 platelet count 70,000μL for Pegasys and platelet count 100,000μL for PEG-Intron will then proceed to Part 2. In Part 2, subjects will receive an additional 8 weeks of SB-497115-GR or placebo administered daily with antiviral therapy. 