Unless you know who gave you a bad reference, it will be difficult to pin down the past employer. You can go to an employment attorney and have a friendly letter sent to each of your past employers stating the law on references. There are companies on the internet that you can pay to check your references but on the whole, they are a rip off. They don't delve and dive and see who might say what. Go get your free consultation and see what a lawyer will do for you. There is someone out there that is unaware of the law and you can take that person to task after you have proof. I am still amazed at how many people own up to not hiring a person because of a bad reference. You will know better than anyone who might have given you a bad reference. You might just eliminate this person or place from your job references. I know that you would love to find out who said what, but they won't reveal that now. They know that you could sue. A letter from an attorney works.
Another simple solution is to have a friend who has a business call, pretend you applied for a job, and get nosy. That would be a simple way to eliminate the bad apple. This will happen again, so act on the problem now.
[Edited by Always searching on 04-03-2001 at 12:10 AM]