* Norway claims fourth successive men's Super-G
* Czech wins snowboarding cross after rivals tumble
* Second cross-country gold for Sweden
* Russian skier serious but stable after breaking back
* Russians outraged over disallowed hockey goal vs U.S. (Adds Swedish cross-country gold, Bode Miller, Samkova quotes)
By Mark Trevelyan
SOCHI, Russia, Feb 16 (Reuters) - Norway's Kjetil Jansrud sped to Olympic gold in the men's super-G alpine skiing on Sunday and Czech Eva Samkova won the women's snowboarding cross after yet more tumbles on the testing course where a Russian skier broke her back a day earlier.
Skicross racer Maria Komissarova, 23, was in a serious but stable condition after an operation lasting more than six hours on Saturday to insert a metal implant in her back.
Doctors said it would take three or four days to know how successful the surgery had been.
On the ninth day of medal competition, Sweden won their second cross-country relay gold when they prevailed in the men's 4x10km event, ahead of Russia and France.
Dutch speed skater Ireen Wust was aiming for her second gold of the Games, in the women's 1,500 metres, and French biathlete Martin Fourcade was favourite to get his third in the 15km mass start.
But many Russians' thoughts were still on the ice hockey action of the previous day, when a late disallowed goal cost the host nation victory over arch-rival the United States.
In a rare moment of political unity, supporters and opponents of President Vladimir Putin came together on Twitter to express their outrage after the Americans won in a shoot-out.
"The puck was in the goal. What an abomination. Cheating before the whole world! Disgusting!" wrote Alexei Pushkov, a senior pro-Putin member of parliament after the score was wiped out because the goal had been shifted from its mooring.
Prominent gay activist Nikolai Alexeyev, at odds with Putin over a law banning homosexual propaganda among minors that overshadowed the build-up to the Games, was left in shock: "There's a huge scandal in the hockey tournament. The American referee didn't allow the Russian goal. Damn!"
After pre-Games criticism over human rights and the estimated $50 billion cost of bringing the Olympics to Sochi, Putin can so far take satisfaction from an event where Russia has shown a friendly, welcoming face to the rest of the world and the sporting action has yielded plenty of drama.
On the Rosa Khutor piste in the Caucasus mountains, Jansrud secured Norway's fourth successive Olympic men's super-G win, while 36-year-old American Bode Miller tied for bronze with Canada's Jan Hudec, to become the oldest ever Alpine skiing medallist.
Miller's team mate Andrew Weibrecht captured a surprise silver medal after starting 29th, with all the favourites gone.
"When Andrew came down he scared me," laughed Jansrud. "It was a little too exciting. My legs were like jelly there for a second but I knew I had finished very strong."
Miller, who now has six Olympic medals, was overcome with emotion as he remembered his younger brother Chelone, a promising snowboarder who might have been at the Games but died of an apparent seizure last year.
"Losing my brother this last year was really hard for myself, my family, our whole community," he said. "To have things go well today, as well as they did ... everything felt pretty raw and pretty connected. It was a lot for me."
Czech athlete Samkova, sporting a fake moustache drawn on her top lip for good luck, avoided the rough and tumble of the pack in the thrilling snowboarding cross event where racers go head to head down a twisty course full of bumps and jumps, jostling with their rivals to find the best line.
"It's a lucky moustache. Today it's in national colours," she said of her facial adornment in red, white and blue.
Defending champion Maelle Ricker of Canada and 2006 silver medallist Lindsey Jacobellis of the United States were eliminated in the heats after taking tumbles on the Extreme Park course.
Dominique Maltais of Canada took silver to add to the bronze she won in Turin eight years ago, while French teenager Chloe Trespeuch was third.
Earlier, two more racers were stretchered off after bad falls - Norway's Helene Olafsen with knee damage and American Jacqueline Hernandez with concussion, though neither of the injuries was serious.
After 54 of 98 events, Germany led the medals table with seven golds, followed by Norway and Switzerland and five. Hosts Russia were tied on four with Canada, the United States, the Netherlands and Poland - who have no silvers or bronze.
In late-night action on Saturday, Poland's Kamil Stoch snatched the men's large hill ski jumping gold medal from Japan's Noriaki Kasai, overhauling him with the last jump of the competition.
But the silver was a triumph for the 41-year-old Kasai, who was competing in a record seventh Winter Olympics but had never before won an individual medal.
"It is hard to describe. What can I say? It is like a dream to me," Kasai, the oldest ski jumper to win an Olympic medal, told reporters after being cheered and applauded by a gaggle of excited Japanese TV crews.
"All these years I was disappointed by the Olympic Games. Today I just had to do it." (Additional reporting by Reuters Winter Olympic team in Sochi and Rosa Khutor; Editing by Peter Rutherford)