Javascript - issues with replacing text

I am having issues with the replace in my javascript page...I have text that I am editing that is very long....its seems that the replace method doesnt work in large text segments

below is what I want replace...but the variable pre_final_decrypt is a very large character string for encryption..as you can image encryption strings can be very large...thanks


        var v_start_superhero = pre_final_decrypt.replace("!!!!!!!!!!!COMIC_BOOK//////////", "");