Reston-based comScore Inc had record fourth-quarter revenue but swung to a quarterly loss on acquisition and severance costs. The Internet tracking gcompany reported revenue of $51.2 million, up 52 percent from the fourth quarter of 2009. It posted a net loss of $494,000, or 2 cents per share, compared with net income of $1.6 million, or 5 cents per share, a year earlier. ComScore (NASDAQ: SCOR) made several acquisitions in 2010, including ARS Group, Nexius Xplore and Nedstat NV. For the full year, comScore had revenue of $175 million, compared with...