Just from reading their past posts, the Incarnation means little to these people and they like to gloss over the Crucifixion and glorify the Resurection.
Their faith is only based on their own opinion of what the Bible says, although they all say they are guided by the Holy Spirit, who evidently tells different people different things so everyone can be confused, I guess.
They seem to think that being “saved” is the end of the journey and not the beginning. They think that being “saved” is the only goal. They think that serving God, willingly, consciously is believing that you are “working out your salvation” and so we must not believe that we are saved solely by the Grace of God.
Some of them even believe that God created some to be damned and some to be elect and that you have no choice in the matter. Nope, no free will, the tyant God will force you to go to heaven whether you want to or not, whether you sin badly or not and send you to hell no matter how badly you would like to go.
I'm pinging Mad Dawg here, too, because I'm likely to get in over my head! ;-) I really think a lot of the misunderstanding stems from difference in how we understand eternity: for Catholics (and some Protestants, but I can't speak with authority here), we are creatures within time, but time is itself a creature, had a beginning and will end (at least as we know it); it's an aspect of the created material world. But God (and in some way the angels and everyone in heaven -- or, I guess, hell) is outside of time. The theologians usually express it by some form of "to God, everything is in the present," which is of course inadequate, but we do what we can.
To many Protestants, eternity simply means a long, long time. Which puts God in time (even if it's an infinitely extended time); whereas, we can't even say that "God is in eternity," because that would make "eternity" greater than God (as if it can contain Him). Maybe we could say "eternity is one aspect of God" or something like that and it wouldn't be too misleading. (Mad Dawg, anything to say here?)
This naturally affects understanding of the Incarnation. They insist that Mary is only the mother of Christ's human nature, that Christ took his human flesh from Mary (true enough as far as it goes). This sounds, of course, like the Nestorian position, but the Protestants who argue it don't know enough theology to be actual Nestorians. The hypostatic union can't be split like two layers attached by a Velcro fastening. God is immutable, so it can't be that one day God decided to change into a two-part Being. (Mad Dawg, I really am getting in over my head here!)
Anyway, this is also why the Sacrifice of the Mass doesn't make sense to them. To us, Christ-- in Himself and in the Mass -- is the nexus between time and eternity, so that we understand the Mass as allowing us to be present at the Eternal Sacrifice of Calvary. To them, the crucifixion happened only once, totally bounded by time, and it's over! All this, of course, is a Mystery; I think Catholics are more comfortable -- or at least less uncomfortable -- with Mystery than Protestants.
I think this also comes into play with the Protestant notion of predestination. Everything, including God, can be described linearly.
Anyway, that's as far as I've thought about it so far.