PARIS (Reuters) -- Amelie Mauresmo once more crumbled like a clay figurine at the French Open on Sunday, beaten in the fourth round by a Czech teenager nearly 10 years her junior.

Nicole Vaidisova embarrassed the world number one 6-7 6-1 6-2, exposing the fragility of the 26-year-old Frenchwoman who has never gone beyond the quarterfinals of her home grand slam.

Earlier Dinara Safina upset fellow Russian Maria Sharapova, women's fourth seed, while Roger Federer, David Nalbandian Justine Henin-Hardenne and Kim Clijsters strolled into the last eight.

Switzerland's Martina Hingis was locked at one-set all with Israeli Shahar Peer when bad light stopped play.

Mauresmo's latest failure, however, overshadowed it all.

Vaidisova lost 6-1 6-1 to the Frenchwoman at the same stage of the Australian Open which Mauresmo won in January but nothing comes easily to her in Paris and after leading 5-2 in the first set her strength seemed inexplicably to drain away.

She scrambled through the tiebreak but after that barely won a game as Vaidisova's fearless hitting left the 15,000 mainly French supporters packed into the steepling center court dumb with deja vu.

By the end Mauresmo's face was taut with tension and Vaidisova put her out of her misery with a conclusive backhand winner. Almost guiltily, the 17-year-old Czech dropped her racket and fell to her knees as if to ask forgiveness from the crowd.

"It's a little bit difficult to really explain and know what exactly happened to me right now," Mauresmo said. "It's a difficult moment, but that's the way it is and it happens.

"I just played with less intensity, so that she was able to come in and play much better. "Maybe people shouldn't expect much of me on clay." Mauresmo could probably learn something from her conqueror. "I was in my little zone," said Vaidisova, whose next opponent is American Venus Williams. "It's my first ever quarterfinal in a grand slam so I'm very excited."

Safina won a ferocious Russian catfight against Sharapova to reach her first grand slam quarterfinal too.

She looked beaten when she trailed 5-1 in the final set but the 20-year-old rattled off six successive games to complete a spectacular 7-5 2-6 7-5 victory over the 2004 Wimbledon champion on Court Suzanne Lenglen. "She picked up her game a little bit and mine went down -- it's not a good combination," a miffed Sharapova said. "You go into a different world and you make dumb decisions."