The Immaculate Conception does not refer to the virgin birth of Christ, but rather is a uniquely Roman Catholic teaching. It teaches that the grace of Christ's sacrifice on the cross was "preveniently" given to Mary at the time of *her* conception in the womb of Anna.
It thus teaches that Mary was born without original sin of any kind and furthermore was specially filled with the Holy Spirit from the time of her conception -- filled with so much grace that she had and has "extra" grace that she can dispense to the rest of us if we pray to her and ask for it, etc.
The Orthodox Church does not accept this teaching. We believe that Mary was conceived in the same way that any other person was. We believe that the "original sin" that man is born with is the tendency to corruption, sin, and death. We believe that Mary was born with all of those things just as we are. We do not believe that a man is born with original guilt such that his default setting is to go to hell, but rather believe that we sin because we choose to, giving in to the innate corruption and weakness within us. It is our sins that we actively commit that turn our faces towards hell and the devil. We need the grace of Christ to be forgiven for all of our sins.
What we do believe is that from the earliest moments of cognition in her life, Mary chose to turn her face toward God. The Church teaches that she was born into a highly devout immediate and extended family, and that she was reared in purity. Someone once said that the whole history of the world, the whole history of that golden thread that runs through the Old Testament, is to tell us the story of how all of history came to a point with this family, this couple, this girl. The girl who would change the world because of her purity and obedience to God.
In other words, the Orthodox Church believes that Mary had no spiritual tools at her disposal other than the ones we have. This is what makes her sinlessness so remarkable, and what made her a worthy vessel for bringing Christ into the world. It is also what makes her an example for us that we can follow. If she was a "superwoman" filled with so much grace that it was impossible for her to sin, we can hardly use her as a model for our own lives, can we?
The fact that she was subject to the effects of original sin is borne out by the fact that she grew old and died just like everyone else. I would note that there are some Catholics who believe that she did not die, but was assumed into heaven without having died. This is a logical outgrowth from the idea of the Immaculate Conception -- if she was not subject to original sin... how could she die?
Agrarian, that was very nice, and it simply reinforces what I had said (less elegantly) earlier. However, one might ask the same question of why would Jesus die, for He was free of any sin. The answer I got in the past on this question was simply: because He chose to.
MARY BESTOWS GRACE!? And to think that priests forgiving sins made me crazy. :) I thought you prayed to Mary for a prayer, not to be given something from her on her own authority.
This view also appears to disagree with the Protoevangelism of James that I was kindly shown earlier. What do you say about the grace Mary was shown at three years old?
What we do believe is that from the earliest moments of cognition in her life, Mary chose to turn her face toward God.
You said that Mary was conceived and born in the normal way. Also, you said that she was given special grace at conception, which must be what makes it immaculate. You later say that it was always possible for Mary to sin, but from her first moment of cognition she chose not to sin. I am sure you are familiar with children and their propensity to always choose never to sin. :)
What I'm leading to is that if Mary was always subject to sin, but never chose to even as a child, then how could that not be the act of God controlling her? Mary could not have had a free will and chosen to never sin, even with her super grace. The super grace must have overwhelmed her, else she would not have been human. Adam and Eve were also presumably not born with the sin nature, yet Mary beat them both out. What was the only difference? Super grace. How can you say that she used free will? On your terms, Adam used his free will, and we all know what happened.