Cum haruspex in templo cenaret, rex ipse appropinquabat.
My problem is with the part in bold, firstly the cenaret, an imperfect subunctive does not agree with haruspex. (Or does it? I could be wrong.) Obviously it will not agree with templo (have you ever heard of a temple eating its dinner?). The problem continues, as templo is either dative, or ablative. Assuming my teacher (this an exam revision exercise by the way) made a mistake with either cenaret or haruspex, so we can reasonably assume that the soothsayers were eating in the temple, even then neither dative (by or to the temple) or ablative (by or with the temple) make sense in the context of the sentence.