Prot# A431-1002: Phs II, Dbl-Bld, Rndmzd, Plcbo Cntrl'd Study of 2 Doses of Capravirine (AG1549) in Combt'n w/ VIRACEPT? & 2 Nucleoside Reverse Transcriptase Inhibitors in HIV-Infected Patients Who Failed an Initial Nonnucleoside Reverse Transcriptase Inh