Pawnee, Oklahoma, held a non-partisan election for Mayor on April 5, 2011. Chris Linder won. However, because he had a past felony conviction in Arizona, he cannot be sworn in. See this story. Now the city will need a special election to fill the vacancy. Thanks to Richard Prawdzienski for the link.
Linder did not know that his past felony conviction would disqualify him until after the ballots had been printed. Then he tried to get a pardon from Arizona, but Arizona officials refused.