The home side responded in style when Tomas O'Leary took advantage of poor defending by Richard Fussell to cleverly kick the ball through for Howlett to gather and score in the corner, O'Gara missing the conversion.
The Blades had been chasing victory with substitute Marcus Bent guilty of missing a gilt-edged chance from Bjorn Helge Riise's corner on the edge of the six-yard box while Joe Mattock lashed a 20-yard volley wide.