The Problem of Evil in Reincarnation

Karma gives answers to why innocent people are suffering in this life. It's because of their past life's sins. Can some one tell me the flaw in my logic? I really want to know. We didn't have the time to go in at length to the christian answer to the problem of evil. Even if god allowed, not positively willing, but allowed some one to suffer innocently in life, god can vastly more than make it up to that person in the next life. This life is a tiny blip in an infinite future life. And consequently, saint paul talks about how the sufferings of this life are not even worth comparing to the great weight of glory that