...is the same problem in finding the historical Moses or the historical Mohamed. Everyone uses snippets from the historical texts to reenforce their preconceived notions of who or what these people were.

In the case of the "Virgin" Mary, I think an objective reading of the history of the gospel of Matthew, and the various fragments, will come to the conclusion that these texts have not been altered in any significant fashion from their originals. The NT authors were very much influenced by Greek thought and the Greek translation of the Torah. The Septuigint had Isiah 7:14 translated as the english equivalent of "virgin", though the original Hebrew word is "almah" which according to most scholars just means something along the lines of "woman of marriagable age".

Of course, this brings up more questions than it answers. For example, why were these people using the LXX (Septuagint) with it's 70 books, instead of the 60 books of the Jewish canon? (Hint, the Jewish canon was given 190AD and was a function of trying to lock out greek thought). More importantly, can we admit that Matthew may have been written based on translated text? (Hint, Biblical literalists are going to be rather irritable on the subject).

The age of analysis for the Historical Jesus has actually passed by (it was very intense prior to the 70's). Nowadays, there are not many that are particularly interested in an exhaustive search. And those that tap into the work have their own agendas.

I say that Schwitzer had it right: We are never going to find the historical Jesus, so we mind as well start helping our fellow man (He went and practiced medicine in Africa after a very intense carreer in Bliblical studies).