Michael:

Sorry, I have no idea what is going on. The earliest version of Matthew in the NET Bible I have also has virgin. My version is of the New Testament alone, so it is an early edition (though not perhaps the earliest). It was done before the Old Testament was released. The "First Beta edition" of the whole Bible also has virgin. What might be going on is that the NET rendering of the Hebrew in Isaiah 7:14 in this Beta edition was young woman, reflecting the most likely contextual meaning of that Hebrew term in that passage. What many people do not think about is that many young women of that time were virgins, which is why there is discussion about what that term can mean and why a more exact sense can be given in Matthew and in the LXX. The NT usage works with what is called mirror (or pattern) prophecy where a short term event is repeated (and often enhanced) in a susequent realization of the pattern. In this case a young woman giving birth to a child picturing God with us (the meaning of the name Emmanuel) in the time of Isaiah pictures and prophecies a virgin (enhancement 1) giving birth to GOD WITH US (enhancement 2), Jesus.

dlb