The purpose of this study is to evaluate antiretroviral activity of up to five different oral doses administered for two weeks of bevirimat versus placebo in HIV treatment experienced patients, who have documented genotypic resistance to at least one major mutation from the IAS-USA list (2007)of resistance mutations for NRTIs, NNRTIs, or PIs. Patients will also be monitored for side effects, and the pharmacokinetics of bevirimat will be determined.