Some feel it was from Byzantine times, or later. Freund, seemed pretty certain it was from Roman times, but nothing new on this since 2003.
It's strange, that something like this would not be a certainty. I found this at Yahoo, which is more of the "debate" really:
http://answers.yahoo.com/question/index?qid=20070711064836AAw24Xd
It does strike me as strange that Nazareth would be "insignificant", if in fact the prophecies of Jesus coming from Nazareth are accurate. It would suggest to me that the Jews would have been looking to Nazareth constantly, for their Messiah.