Have you all called the county or state that placed the tax lien? Maybe they still have on their records that they are still married? If that's the case it would go on both their credit reports. Have you checked all 3 credit reports? The ppl who placed the Tax Lien would be the ones who are still reporting to the credit reports. Start with them and then see about getting the info removed once they stop reporting.

I've had weird stuff I had to fix. I had my credit card on my father-n-law's credit report. They had gone by my mailing address and not SS# when reporting to credit. You get a free credit report a year, everyone should check their reports to look for mistakes and ID thift.