HELP????? Credit checks - mortgage company dispute

Hi all, after some advice.
i today applied for a decision in principle with my mortgage broker to a building society. The decision was then referred to the underwriters which later came back declined due to 'oustanding adverse credit'. both my broker and i have been torugh all credit reports and there is nothing - not so much as a blip.

So he was just as confused as i am - he then went back to the building society who stated 'it is registered at one of the linked address connected to me' but they wont say which one. Again confused!!!! hes been through the report with a fine tooth comb. this lender uses equifax to do their searches so he suggested i call them up as they will be able to tell me (although there is nothing on my report in front of me)

So i called equifax to explain the situation. They checked also and told me all my payments are always on time and i have no outstanding debt nor adverse credit history. confused.com??????

So my question is where has this building society got this info from and what can i do about it when even the credit reference company say there is nothing on my records and i have the report in front of me to prove it???


HEEEEEEELLLP!!!

thanks