Note: I am cross-posting (actually, emailing) this to 
bit.listserv.catholic while main posting goes to 
soc.religion.christian.

[Quotations omitted.  This is in response to a question about
the Immaculate Conception.  I explained it, but left justification
up to our Catholic readers.  --clh]

There is no direct reference in the Holy Scripture except for the
mention of Mary's _blessedness_/full of grace in the "Annunciation" by
Angel Gabriel in Luke 1:26-28

 And in the 6th month the angel Gabriel was sent from God unto
 a city of Galilee, named Nazareth.  To a virgin espoused to a
 man whose name was Joseph, of the house of David; and the virgin's
 name was Mary.  And the angel came unto her and said, _"Hail,
 thou that art highly favoured, the Lord is with thee: blessed
 art thou among women."_

Now, now, hold that line of thought - "the Lord is with Mary &
blessed art thou among women" - while you read on....

In the book, "First Lady of the World, A Popular History of
Devotion to Mary" by Peter Lappin:

The _Immaculate Conception_ matter is really far more complicated
than the _Assumption_.  This arose in 430 AD.  It is quite possible
that the feast of _Mary's Conception_ under the title "The Conception
of Saint Anne", originally commemorated the _physical miracle_ of
a woman _beyond the age_ of child bearing, conceiving a daughter,
just as Elizabeth had conceived John the Baptist.  A transfer in
emphasis from the physical miracle wrought in Anne to the miracle
of grace wrought by God in the soul of Mary was _logical_.  Mary
is the incorruptible timber "out of which was hewn the _tabernacle_
of Christ's sinless body"; she is "God's Eden, in whom there is
no tree of knowledge, and no serpent that harms."  Her perfect
beauty and spotlessness find their exemplar in Christ, her
purity in that of the Father.  At the time of the Council of Ephesus,
she was hailed as "innocent, without blemish, immaculate, inviolate,
spotless, holy in soul and body, who was blessed as a lily from
among thorns, unlearned in the evil ways of Eve".
...
At the end of the thirteenth century, an Irish Franciscan,
John Duns Scotus (1266-1308),...God maintained that it was a 
greater thing for Him to preserve His (the Son) mother from all
sin _than to use His power to clease her from it later_.
...

Now let's go to the discussion of baptism and original sin.
From "Pocket Catholic Cathechism" by John A. Hardon:

Baptism -
Concupiscence Remains after Baptism.
Concupiscence or the tendency to sin remains in the baptized
but since it is left to provide trial, it has no power to
injure those who do not consent and who by the grace of
Christ Jesus, manfully resist (Canon 5).

Original gifts of Adam and Eve before their fall:
In the light of the foregoing, we see that our first
parents were originally gifted three times over:
-They had the natural gifts of human beings especially the
 power to think and to choose freely.
-The had the _preternatural_ gifts of bodily immortality
 and of integrity, or the internal power to control desires.
-They had the _supernatural_ gifts of sanctifying grace,
 the virtues of faith, hope, and charity and the corresponding
 title to enter heaven.
By their disobedience, they lost the _supernatural and
preternatural_ gifts entirely, and were weakened (without
losing) their natural capacity to reason and to choose
freely.

Baptism restores the _supernatural_ life lost by Adam's
sin.  It _does not_ restore the _preternatural_ gifts
but gifts as a title to a glorified restoration of our
bodies on the last day...

Going back to _Immaculate Conception_
(I am not sure if this interpretation is in any other
books but it may be another contribution to the 'puzzle'):

Given the miracle of St. Anne bearing a child at a
non-childbearing age, AND Christ was not yet born 
AND _there was no baptism yet_ on Mary's birth but
STILL, the Angel Gabriel's greetings was:
"Hail Mary, full of grace, the Lord is with you.
Blessed art thou amongst women".

Even Mary was confused about this greeting.

Mary could very well have possessed all of the
_treefold original gifts above_ given to our first
parents (Adam and Eve before their sin):
    Hail Mary (Example of praise given by the Angel Gabriel)
    Full of grace (natural, preternatural, supernatural)
    The Lord is with you (At those times, God would
                definitely want to be with those He
                has made _blessed_)
    Blessed art thou amongst women (that says it all)

At the conception, God made Mary _full of grace
and blessed_ as the 'tabernacle' for the coming body
of Christ and so,

Immaculate Conception of Mary is true and Mary still
has maintained her Immaculate Heart. 