12/9/08 updated 12/10/08
Calling problems, "challenges", is due to the influence of the false gospel of Positive Thinking and the pervasive effects of the Human Potential Movement in society and the Church.
Biblically, a problem, whether trial or tragedy, is something in which we trust our Lord Jesus while facing up to the truth. We call it what it is, a trial or a tragedy, suffering, but we know Romans 8:28 is true.
The Human Potential philosophies try to get people to positive confess themselves through problems by their own mind power.
For a Biblical view of trials, tragedies, and suffering see 1 Peter 1 and James 1 and Ephesians 3:10, 11.