I have to agree with Ding on this one. I came across this argument by Ehrman about a year ago and when I looked up the John 3 in the NWT it seemed perfectly reasonable that Nicodemus could be confused by being "born from above" rendered in both places.
Now it could well be meant as word play in the Gospel of John under the mistaken belief that they were speaking Greek. But there's no way to establish from these two scriptures that Jesus and Nicodemus weren't speaking in Aramaic.
Whether the Greek word is rendered as "born again" or as "from above" . . . or even if it's rendered as both "born again" and "from above" in different places - the statement is still confusing. And Nicodemus line of questioning is completely reasonable.
I've learned to be very cautious with Ehrman's claims and lines of reasoning - you really have to do your research. He does a lot of sloppy work. Carrier has pointed this out numerous times: http://freethoughtblogs.com/carrier/archives/1026