If you signed a personal guaranty, you are obligated to it; if your ex-husband has not paid, the lender/creditor can seek payment from you.If they do, you could file bankruptcy to discharge the debt, but will most likely still end up paying some of it--bankruptcy usually reduces the amount you pay, to dimes or even pennies on the dollar, but usually does not wipe out debts completely--ESPECIALLY if you have the money (income and/or assets) to pay the debt, but just don't want to (the results of your bankruptcy filing will depend on the balance of your debts vs. income and assets; bankruptcy is designed to help people who can't pay their debts, not merely people who'd prefer to not pay). You don't have to file bankruptcy "in advance" but can wait until (and if) the lender proceeds against you).You could also, if you are sued for the money, sue your ex to get  from him the amount you have to pay out due to his breach of his obligations; of course, if he doesn't have the income or assets to pay, that will not help you.