From The LA Times:
I just finished paying off my last credit card and checked my credit report as I am now separated from my wife. I found we had one joint account that she had not been paying. There are two stretches of five months each of no payment. Read more
I immediately called up the creditor and paid off the balance and the creditor closed the account due to the lack of payments. This one account killed my credit score. I also found two old accounts on my credit report that are both still active but I have not used them for years. Both accounts are in good standing.
The article points out that failure to pay a joint account hurts both parties' credit scores, even if a divorce decree assigns responsibility for the debt to the other party, because creditors do not have to pay attention to such arrangements.