What can I do about my mother's estate debts?

My mother passed away in October 2012. I am executor to the estate. I was contacted in early January by a member of her HOA indicating fees were past due. At the time, I was unaware this HOA existed, as it's a subset of a larger HOA I knew she paid into. I said I would need to review financial records to verify whether the amount was indeed past due. I asked for a detailed accounting of what they believed was due, a copy of the HOA covenants, so I could see and verify the fee schedule, and then info as to whom payment was to be made. A few weeks later I received only a hand written note of what was due. Nothing else. I was planning on getting in touch with them to ask again for the other materials. Before I had a chance, I received a voice mail threatening a lien against the property. Do they even have the authority to do that? Delinquent dues (if legitimate) now date back 8 months, and approx. $540. But as I was just contacted 60 days ago, have no details of covenants, or even their lien policy, can they actually do anything yet?