Am I responsible for this debt?

I guess, you are not responsible for his unpaid debts as long as you are not holding those jointly. The creditors can't come after you or your current husband for the ex-spouse's loans, though it needs to be tallied with the existing state laws.

But if the credits were jointly issued to both of you, then unfortunately the creditors have the right to come after you for the unpaid amount.

Were you listed as a co-applicant on the Discover account? If you were, then you are responsible for it, at least in part. But...

You said this was in 1999? It's dropped off of your credit report, correct? It's probably past the statute of limitations, too. What state do you live in, so we can check that? If it's gone past SoL, they can't sue on it, so they'd be all bark and no bite at this point.

Is this harassment from a collection agency, or directly from Discover? Either way, I'd send them a demand for validation. You can find a good template here:

http://www.debtconsolidationcare.com/collection-agencies/better-structure.html

Who is the agency collecting for this? I'm wondering because it sound strange as the two main things I'm seeing wrong here.
1. Bankruptcy, the two types I am familiar with work like this either A. your debts are discharged and you owe nothing, or B. your debts are discharged and you pay courts what you owe while no interest, late fees, etc. accrue.
2. The cards became the sole property of your ex in the divorce, if this was included in the decree then that means that your responsibility has been absolved.

hang on guys--we are missing some things here.

The divorce happened back then. We dont know how much longer he used that card. he could have used it within the last few years and still rack up a high balance. The SOL is entirely dependent on the date of last activity on the account. We dont even know if he definitely listed this card on the bankruptcy. If he didnt, then his BK doesnt have any effect on this debt.

To the OP, was there anything at all in the divorce decree that gave him the credit card? A lot of times, debts and property are divided and statements to that effect are included in the decree--check to see if there is any such assignment by the court on this account. If there is, then you can tell whoever is calling to go pound sand. If not, then you need to find out the date of last activity on that account. This would be the last date he made a payment on it. If he put this on his BK way back then, chances are pretty good that the SOL has expired. But you need to know for certain.

A divorce decree wouldn't absolve the legal responsibility to the card. If needed you would have to sue the ex spouse to resolve the account. The creditor and collection agency won't care about a divorce decree. They will go after who the accounts belong to.

Now, unless you are a cosigner on this account meaning when he signed up for it you both used your social security # and his, you will also be responsible. However if you did not then you shouldn't have to worry. Send a C&D letter to whom ever is calling you and I would also explain that because your personal information isn't attached to the account you are not responsible for any portion of this debt that your ex- created.