NOW HERE'S THE NEWS: The new John Cougar Mellencamp version of "Under the Boardwalk" that you've been hearing on rock radio isn't on his "Scarecrow" album. It's only available on the B-side of his current single, "R.O.C.K. in the U.S.A." . . . And speaking of B-sides, the new Prince single, "Kiss," has a flip side that's not on "Parade" called " or $" (translated as "Love or Money). . . . London's teen dreams, the Spandau Ballet, have split with Chrysalis Records--after months of legal difficulties--and are looking for a new home. Needless to say, several major labels have already expressed interest. . . . Ex-Styx vocalist Dennis De Young is busy in the studio, producing a pair of songs for an upcoming Liza Minnelli album. . . . And X's John Doe will play a rare solo acoustic set Thursday night at the Lhasa Club. He'll follow an acoustic set by the always unpredictable Holy Sisters of the Ga Ga Da Da.