I know I'm jumping in here late, but I know one of the main objections to Mary's virginity revolve around the the word "until."
Here are some other examples of when brethren doesn't mean siblings and until doesn't mean a change happened afterwards:
1 Timothy 6:14 says, "That thou keep this commandment without spot, unrebukable, until the appearing of our Lord Jesus Christ." (What? After that it's going to be one big orgy? I don't think so!)
Genesis 8:7: "the raven "did not return until the waters were dried up" (the raven never returned even after the waters were dried up);
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Deuteronomy 34:6: "and no one knows his [Moses'] grave until this day." (Moses' grave was never found) [/FONT]
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Luke 1:80: "[St. John the Baptist] was in the deserts until the day of his manifestation to Israel." (St. John stayed in the desert afterwards, too) [/FONT]
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1 Corinthians 15:25: "For He must reign until He has put all enemies under His feet" (Christ will reign forever and ever!) [/FONT]
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1 Timothy 4:13: "until I come, give attention to reading, to exhortation, to doctrine" (Trust me, St. Paul gave a lot of attention to doctrine after he came!) [/FONT]
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Revelation 2:25-26: "But hold fast what you have until I come. And he who overcomes and keeps My works until the end, to him I will give power" (we should hold fast and obey even after Jesus returns) [/FONT]