Immigration Site

hello
my wife she a us citizen and i apply for a green card based on marriage im worried about my case.
i send my papers at December 2010 but the immigration office send me the recite that they receive the paper at Febuary 2011 i had finger print at the same month i recieve my work permit visa at murch but it come with a wrong country of birth so i send it back to the immigration office to be fix i had the interview at 4.27.11 and the interview was good the officer ask us questions for 40 min in the end he told us thank you very much for our time and we left the room its been a month and i call the immigration office and they told me" your case is pending if thet approve my case or need more information they will send me by mail "
and i still didnt receive my new work permit visa or any thing from them...
im worried someone know now what im waiting for?
i know that usually after 2 week after the interview you recivee the note that say "welcome to america"
i didnt recive any thing yet.
how long its take to have an answer?

They can approve it from at the interview on the spot to several months, your case sounds complicated and it seems like is going to be thoroughly investigated, there is nothing you can do except to wait for an answer.

what you mean by thoroughly investigated?
second interview?
name check ?

thank you for your help

possibly all the above or you may be surprised and you get your greencard in the mail.