Amprenavir/Ritonavir or Saquinavir/Ritonavir in HIV-Infected Subjects Following Failure With Kaletra as Their Second Protease Inhibitor

Inclusion: * Subject must remain on current antiretroviral therapy during screening until a new regimen is initiated. * Subject demonstrates reduced susceptibility to lopinavir. * Subject's two most recent viral loads obtained after at least 16 weeks of lopinavir/ritonavir therapy, and while still on Kaletra therapy must be at least 1,000 copies/mL. * The Kaletra regimen must be the subject's second PI containing regimen and must not contain any other PIs. * Subject is at least 18 years of age. * Subject has not been treated for an active opportunistic infection within 30 days of screening. Exclusion: * Subject has a history of active substance abuse or psychiatric illness that could preclude compliance to the protocol. * Female subject pregnant or lactating. * Use of an Investigational drug within 30 days prior to the initiation of drug dosing. * Subject is receiving systemic chemotherapy. * Subject has a history of acute or chronic pancreatitis.