The problem of suffering causes a lot of confusion for people. The question tends to be formed in the fashion, "if God exists, why does bad thing X happen?"
This is troubling to many people who believe in God, and Christians are no exception. Since I have come to the conclusion that Christianity has the greatest merit in terms of explanatory power and logical cohesion, and given my existential experiences, I have also had to deal with this issue as a Christian.
The question is much easier to address if you already believe in God.
Essentially, at worst a believer considers suffering a mystery that will be solved in the future, when all things are restored to a right relationship with the Thing Maker. I have a fair degree of acceptance with the notion of suffering in the world. While suffering causes me to feel compassion and compels me to what action I can and do take, it does not lead me to question the existence of God.
If you do not believe in God, or just never got around to addressing the issue of the meaning of life and the reality of the hereafter, the question "why does X happen" can be posed in genuine intellectual curiosity. However, it can also be an emotional response. Since both the intellect and the emotions are involved in belief, I believe such queries are valid. But the question, asked two different ways, are essentially two questions.
An intellectual "if God why X" can be addressed with logic and philosophy. It is a general, "why does X happen at all?" question. An emotional "if God why X" would likely stem from personal loss and pain, and it is likely a far more restrictive "why did X happen to me or my loved ones?" type of question.
At this point, I seek only to answer the intellectual question. I do not think that personal pain can be addressed just by a post. Personal pain requires a personal response, and the path to healing is different from the path to intellectual enlightenment. It is necessary to take great care to weep with those who weep, rather than to try to answer all the question of a human being in pain. Answers may well have to wait until the tears have subsided.
For the intellectual questioner, "if God why X" can be answered along the lines of my previous post in Philosophy and Religion. Essentially, God is also just (that is, honorable and fair, morally right), and a just God must allow for free agents to choose their own course of action freely. Humans are not perfect, and we do not always desire what is best for all mankind. Thus we see human suffering at the hands of other free moral agents. The rest of creation reflects such a corruption of its intended purpose.
It is my belief that, once a person has had enough history behind their lives, they may begin to see the corruption inherent to their beings and seek something better and purer. The Creator will allow all creation to run its course as well, and then when He correct Creation and restores it to its origianl beauty, then every being that exists will be able to fulfill the original destiny it was created for, and the created will also bring no more harm or pain.
But I believe we can begin that journey now. Restoration is available through God, and you can experience that now.
If there are specifics that anybody would like to address, let me know and I will respond systematically.