The Sunscreen Controversy: Sunscreen, skin cancer risk, and malignant melanoma? What's the deal?

I've heard from many places that sunscreen can lower you chances of skin cancer. Then you hear that the FDA concludes that sunscreen alone doesn't do anything to prevent skin cancer. Then you hear others that say that sunscreen may even increase the likelihood of malignant melanoma, the most lethal of the three types of skin cancer, and that there's a difference between the underlying processes that cause sunburn and malignant melanoma and that stopping sunburn doesn't stop the latter of the two. They say that sunscreen helps prevent the two most common types of skin cancer, but may aggravate the most lethal of the three because of what it does with free radicals in the skin. So, what's the scoop on all this? If you get a sunscreen that not only blocks UVB but also UVA rays and apply it every two hours no matter what, would you still have this problem? What does one do to protect themselves?