The Vikings signed free agent offensive lineman Adam O'Connor on Tuesday. O'Connor started all 10 games he played for Hamburg in NFL Europe last season, helping the SeaDevils to the World Bowl championship last month. Less than a week later, the NFL decided to fold the league after 16 years of competition. O'Connor was signed by the Panthers as a rookie free agent in 2006 and spent time on their practice squad last season. He played defensive end at William & Mary, where he was a three-year starter, but was switched to offensive line when he reached the pros.