[NeoCaveman]

All have sinned and fall short of the glory of God" (Romans 3:23)
As a Southern Baptist, I believe this also pertains to Mary, but I would like to know how Catholics explain it. I am truely not flaming here, just curious.

Good question. I don't have the definitive answer but here are a few possibilities:

Does the "all" mean every single person (as I assume you interpret it) or does it mean all as in no group is exempt. An example of this is too say the "all" could mean no group is excluded (Gentiles, Jews, young, old, men, women, etc.) Of course I am no Greek scholar.

Another is that Mary may have no longer been with us at the time this was preached. OR. If his audience knew her to be sinless there would be no reason to go back and restate it. It would just be assumed that there was no contridiction.

Again, this is all speculation on my part.

[NeoCaveman]

Upon further review of Romans 3:20-23, and really the whole chapter, it seems to me Paul is saying that all have sinned meaning that Jews along with Gentile are not exempt from being sinners. As the context is about salvation by Christ's sactrifice not by keeping the Jewish law.

But that's just my take.