Real Estate Law

We went to a William's and William's Auction in Henderson NV October 29,2008 and were the High bidder on a local property, we were told before the Auction that all of William's and William's properties would be sold free and clear of all Liens, we were also told that we would be told if our bid was accepted within 7 to 10 Business days. We never found out until November 20,2008 that the bid was accepted and the orginal Contract was signed by us to close on or before November 29,2008. There was never any thing signed to change that closing date, and we have still not closed and have since found out that there is a $7301.00 LID on the Property that William's and William's and the Title Company, that they make you use, say is not a Lien, I have been told by the City of Henderson that it is a 1 ST position Lien, but we have been told that they will not pay that off, do we have to accept this, and is our Contract not void since there was never any Addendum done to change the closing date?? Thank You for replying with an answer to this Problem.