I need help from the folks out there who Approve Mortgage Loans?

I need some advice desparately. I am trying to get financed for a loan and am running into a problem and am not sure if I am dealing with people who don't know what they are doing. I purchased a house in 2000. In 2003 my mortgage company (Bank A) sold my loan to another bank (Bank B). Bank B had my loan until 2005 - I sold the house. The finance company that is looking to fiinance me now (Bank C) is asking Bank B to provide them with three years of pay history and are expecting Bank B to give them Bank A's information. Well, Bank B won't give it to Bank C, but Bank A no longer exists. This is holding up the approval for my loan, so my questions are (1) do banks expect all banks to divulge other bank's information like this and is is normal practice (2) why would this hold up my approval everything else is a go (3) should I be looking for another bank or is there validity to what Bank C is doing. Anyone know how this works?