Words:一難Ichi-nan = one misfortune (Ichi: one; Nan: misfortune) /
去ってSatte = leave and (Sa-: one form of Saru = leave; te: connecting joshi particle) /
またMata = again or another example of something /
一難Ichi-nan = one misfortune /
(Jump) Out of the frying pan into the fire. / Misfortunes never come singly.
It refers to describe the situation in which another follows one trouble. As soon as I recovered from my cold, I got this lousy rash all over my face. -- Too bad; it's Ichi-nan Satte Mata Ichi-nan, isn't it?