1. Chart Beat

    April 06, 2006 12:00 AM EDT Mary J sets a R&B/Hip-Hop chart record and T.I. has the biggest hit of his career, plus news on Tim McGraw, Morrissey, Heaven 17 and more. MUCH O'BLIGE: A 5-2 surge for T.I.'s "What You Know" (Grand Hustle/Atlantic) on Billboard's Hot R&B/Hip-Hop Songs chart…