Positive hepatitis B virus, hepatitis C virus or HIV test at screening. Positive serum beta-human chorionic gonadotropin test (females). Women who are pregnant, lactating, or planning to become pregnant. Male subjects who are not willing to abstain from or use a condom during sexual intercourse with pregnant or lactating females. Male subjects not willing to use a condom, plus another form of contraception (e.g., spermicide, IUD, birth control pills taken by female partner, diaphragm with spermicide) if engaging in sexual intercourse with a female who could become pregnant. Male subjects not willing to adhere to these contraceptive criteria from administration of study medication until completion of follow-up procedures.