Updated from 4:57 p.m. EDT After his forays into Mylan Labs ( MYL ), Kerr-McGee ( KMG ) and Blockbuster ( BBI), is activist investor Carl Icahn preparing to storm the towers at Time Warner ( TWX ) ? Shares of the media conglomerate caught fire Tuesday in heavy volume after a television report said Icahn wants to put together a group of investors, possibly including Ted Turner, to force a breakup of the New York-based media empire. The shares closed up 57 cents, or 3.2%, to $18.54 after CNBC reported that Icahn, the onetime corporate raider, was speaking to a number of institutional investors about Time Warner. Icahn's last high-profile move resulted in a shakeup in the boardroom at Blockbuster, the movie rental chain whose second quarter earnings report disappointed Wall Street earlier Tuesday. Trading volume in shares of Time Warner was 40 million shares Tuesday, about twice the daily average.