ST. PETERSBURG, FLORIDA— When the media last year trumpeted the great advances being made against HIV, speculating about cures and even the end of AIDS, the researchers9 own caveats tended to get drowned out. But at a meeting held here last week, emerging data about treatment failures sounded a discordant note that was hard to miss: While powerful new drug combinations are delaying disease and death, they have serious limitations—and clinicians and patients who ignore these shortcomings do so at their peril.