Amprenavir/Ritonavir, Saquinavir/Ritonavir or Efavirenz in HIV-Infected Subjects Following Failure With Kaletra (ABT-378/Ritonavir) as Their First Protease Inhibitor Based HAART

Inclusion: * Remain on present anti-HIV drugs during screening until a new regimen is started. * Have a viral load of at least 1,000 copies/ml on the 2 most recent tests after at least 24 weeks of lopinavir/ritonavir and while still on it. * Have an HIV which shows reduced susceptibility to lopinavir. * Are at least 18 years old. * Are not presently ill. * Have not been treated for an opportunistic infection within 30 days of screening. * Agree not to take certain drugs and agree to inform and get permission from the doctor before taking any medicines, over the counter medicines, herbal medicines, alcohol or recreational drugs. * Agree to use an accepted barrier method of birth control. Exclusion: * Female subject is pregnant or lactating. * Have taken any protease inhibitor other than lopinavir/ritonavir for more that two weeks. * Are taking chemotherapy. * Have a medical problem with their pancreas. * Have been screened for this study within the past 12 weeks. * Appear to be unsuitable in the opinion of the doctor.