Updated from 4:08 p.m. ESTA late-session selloff exacerbated by extremely thin trading volume erased early gains and the major averages finished the post-Christmas session in the red. Lackluster holiday retail results and continuing war worries were cited as the main negative catalysts. After rising more than 100 points by midday, the Dow Jones Industrial Average finished down 15.5 points, or 0.2%, to 8432.61. The Nasdaq lost 4.6 points, or 0.3%, to 1367.89, while the S&P 500 lost 2.8 points, or 0.3%, to 889.66. The session saw some of the lightest trading of the year, with only 716 million shares changing hands on the NYSE and 800 million on the Nasdaq. Retail bellwether Wal-Mart ( WMT) told investors in a recorded update Thursday that it won't meet its targets for the holiday shopping season this year. The world's biggest retailer lowered its same-store sales forecast to a gain of 2% to 3% in December, down from its previous estimate of 3% to 5%. While saying it posted a billion dollars in sales in two of the days leading up to Christmas, the pickup was "too little and too late" to salvage the preliminary estimate. Despite the news, the shares rose 6 cents to $49.76. Generally weak results have retailers increasingly pinning their hopes for this holiday shopping season on post-Christmas returns. Research by Bank of Tokyo-Mitsubishi Ltd. through last Monday put the industry's November and December same-store sales gain at 1.5%, implying one of the worst holiday shopping results in about 30 years. Meanwhile, the Labor Department said new claims for unemployment benefits plummeted by 60,000 in the latest week to 378,000, continuing a series of volatile readings on the indicator. Despite the decline, the four-week average of first-time benefits rose 2,500 to 404,500. Several drug stocks were lower after a study showed that patients taking Pfizer's ( PFE) arthritis treatment, Celebrex, had about the same incidence of stomach bleeding as those using older pain-killers. One of Celebrex's selling points was that it didn't cause such bleeding. Pfizer's shares finished down 4.3% to $30.02, while Pharmacia ( PHA), which co-markets the treatment, was down 4.7% to $40.98. Concerns about the threat of military conflict on both sides of the globe continued to inform investor sentiment. The impact of saber-rattling in Iraq, combined with labor strife in Venezuela, showed up at the pump last week, with the average price of a gallon of gasoline jumping 4 cents. Over the holiday, Venezuela's government put plans in place to end a month-old strike that has crippled the country's petroleum output. Oil traders weren't buying the plan would work, however, and crude oil for February delivery rose 52 cents to $32.49 -- a two-year high.