Mike Borao, the attorney for  heavyweight contender Jameel McCline, confirmed to Boxingtalk that Vitali Klitschko, has called off his comeback bout citing an injury to his back.  Klitschko, a former WBC titlist, was slated to face McCline on September 22, 2007 in Munich, Germany but Klitschko's promoter, K2, informed Borao on Sunday morning that the fight is now off.  Borao had no further comment on the matter. The second half of 2007 was supposed to be a run of great of fights for boxing fans but Klitschko-McCline is the third major fight scheduled for September that has been cancelled or postponed, following in the wake of Fernando Vargas-Ricardo Mayorga and Juan Manuel Marquez-Rocky Juarez.