To discuss this problem I must first break out of my habit of using the English Standard Version, which is a favourite of conservative Christians, and use instead the New Revised Standard Version, which is loathed by them. All will become clear shortly. Here's Isaiah 7:14:
And here's Matthew 1:22-23, discussing the virgin birth of Jesus:
Straightforward misquotation? Well, not exactly. Matthew, who spoke Greek, is quoting from the Greek translation available to him, known as the Septuagint. The original Book of Isaiah was written in Hebrew.
Furthermore, it's not entirely certain that the NRSV's translation is correct. I think it is, but for hundreds of years Bible translators have followed Matthew and translated the word which Isaiah uses, almah, as "virgin". In most other places in the Old Testament, almah means "young woman", and there is a seperate Hebrew word for "virgin". But is it really certain almah could never mean "virgin"?
Certainly the actual translators behind the Septuagint thought "virgin" was correct, otherwise Matthew wouldn't have written what he did. In my opinion this problem is not fatal.
Isaiah 7 doesn't seem to be about Jesus at all; rather, the actual prophecy is that a child will be born (this is around the year 730 BC), and before this child is old enough to know right and wrong, the enemies of Judah will have been defeated.
Again this is probably not fatal: New Testament writers often find hidden meanings in the earlier texts.