Christopher Abbott — who plays Allison Williams’ boyfriend Charlie on Lena Dunham’s HBO series “Girls” — has abruptly left the show, we’ve exclusively learned. The move comes just as his character seemed to be gaining prominence, with Charlie (a k a the cutest guy on the show) reconciling with Williams’ character, Marnie. But sources told Page Six that Abbott and Dunham began butting heads as the critical-darling series entered production again. “They’ve just started work on Season 3, and Chris is at odds with Lena,” a source said. “He didn’t like the direction things are going in, which seems a bit odd since the show put him on the map.” Abbott’s rep confirmed his departure, telling us: “[Chris] is grateful for the experience of collaborating with Lena, Judd [Apatow], and the entire ‘Girls’ cast and crew, but right now he’s working on numerous other projects and has decided not to return to the show.” Abbott appeared in indie movie “Burma” at SXSW last month. And Dunham’s shaken up the writing staff for the new season.