Fr. Stephen at Glory to God for All Things has a very enlightening post on lying.
Bascially he says that we as Christians should not look at lying and similar things from a "moral" perspective. We should not think of the admonition not to lie as merely "one of those rules" that the Church "tells" us we have to do.
Instead, lying is really about not telling the Truth. And, Christ is the Way, the Truth and the Life. Our goal as Christians is to be Truth-tellers.
Lying, of course, comes from the Evil One and does not really exist. Think about it. Lying is telling an untruth--something which, by definition, does not exist. Satan has been called "the father of lies". He tries to be the creator of his own world that does not exist.
Truth, on the other hand, is the ultimate reality. No matter how things may look to us, Truth exists on an existential level. That is why we should not lie. It is not about "God told me and He's going to punish me if I lie." It is about living in Truth--having God's Kingdom within. If we persist in living lies while on earth, we will live forever in lies for eternity. The Kingdom of God is now. We must begin to live in the Truth now, while we still have the gift of this life that has been given to us.
Fr. Stephen begins his article with a teaching from Abba Poelman: Teach your mouth to say what is in your heart.
As fallible human beings, what is in our hearts is often the lies we tell ourselves and others. What then? Should we still "say what is in our hearts"? Yes--in confession! The job, so to speak, of Christians, is to become healed by the Truth. To do this, we must open our wounds to the Light. "Speak what is in your heart" to God's representative on earth in the Sacrament of Confession, and your soul will be filled with Light and gain the strength to carry on in Truth.