Fresh off a trademark skirmish with a local web site, Minnesota Public Radio (MPR) is taking on a bigger target: Al Gore and his Internet television network, Current TV. A suit filed in U.S. District Court in Minnesota claims that Current TV LLC, based in San Francisco, is interfering with the trademark of MPR's mold-breaking music station the Current -- broadcast locally on 89.3 and 88.7 FM, but also transmitted via the internet -- causing confusion among potential consumers. MPR estimates that 37 percent of the Current's listeners are from outside Minnesota, including many abroad, said communications director Jennifer Syltie...