At study entry, patients will be randomly assigned to one of two blinded treatment arms. Arm A receives DAPD plus MMF placebo in addition to their current regimen, while Arm B receives DAPD plus MMF in addition to their current regimen. All patients remain on their current antiretroviral regimen through Week 2. After Week 2, patients who virologically respond are encouraged to remain on blinded study treatment through Week 24. Patients who do not virologically respond are unblinded.