What do you do when the seller doesn't pay prior year supplemental taxes & you receive the delinquency notice?

We closed on our home January 12th, 2009 and we just (June 22nd) received a delinquency notice for supplemental taxes from 2008. I contacted our county tax collector and confirmed the supplemental bill was sent to the owner (bank) before we owned the property. We had $2,275 in seller concessions towards property taxes, but the escrow company won't let me know what what that paid for (too busy to return my calls and e-mails). Should we pay them and call it a loss? Is the bank or escrow company responsible for the taxes? Does title or hazard insurance cover this? Can we sue someone for the unpaid portion? *Note: Our regular property tax coupons were sent to us and paid on time. No supplemental bills were ever sent to our home, none showed up for our property on the tax collector's website, and I even called the tax collector a few months ago and was not advised we had delinquent supplemental taxes.