Renault's Fernando Alonso saw his F1 championship lead cut to 10 points as Michael Schumacher gained an unexpected bonus after the Hungarian Grand Prix.
Schumacher has closed slightly on Alonso
Alonso went out with 18 laps to go, and Ferrari's Schumacher also retired near the end to finish in ninth place.
But he was awarded a point when Robert Kubica was disqualified from seventh because his BMW Sauber was too light.
But Schumacher rued his missed chance, saying: "I am disappointed, but there are still five races to go."
It was a dramatic day at the Hungaroring with both championship contenders appearing, at different times, to be poised to win the race.
That honour eventually went to Honda's Jenson Button, who won in spectacular style, overcoming the tough wet conditions in Budapest.
Alonso had led for much of the afternoon after a breathtaking charge from 15th on the grid.
But a wheel nut failure caused his car to slew and skid into the tyre barriers, leaving Schumacher with the opportunity to slash his world championship lead even further after three straight race wins.
"As I came out of the pits, something broke at the rear end and I spun in turn two," Alonso added.
"We were extremely fast at first. It's a shame. But it happens to everyone."
Schumacher, seven-times a world champion, had been lapped by Alonso after 25 laps but was fighting for second place when he was forced to drive into the pits with a shredded tyre.
With five races remaining and the Turkish GP next up on the F1 calendar in August, Alonso believes he can hold on to take his second successive world championship title.
"The car was really competitive this weekend. We are starting the important part of the championship now, and I am confident."
It was also a bad day for Kimi Raikkonen, who had been on pole but whose race ended with a spectacular shunt into the back of Italian Toro Rosso driver Vitantonio Liuzzi.
"I could do nothing to avoid the collision," said the Finn.
"He really slowed on the racing line and there was nowhere for me to go except into the back of him."