Visa stuck under security clearance

[shabbir_mh]

I'm an Indian applicant and my F-1 visa interview was held on 23rd May 2006 at Mumbai, India. Although my visa has been granted, since my name is a "common name" my application has to undergo security clearance from Washington(this is what the officer mentioned). The officer added that I'll be hearing from the consulate in about 6 weeks time. It has been almost 11 weeks now and I haven't heard from them. When I enquired with the consulate they tell me that they do not have the application with them and it is with some external agency, which they do not know.

Can anyone tell me how long do I have to wait before hearing from the authorities?

Thank you in anticipation.