Nicole Vaidisova of the Czech Republic reacts after defeating defending champion Amelie Mauresmo of France in the fourth round at Wimbledon today. She now moves on to the quarterfinals. ANJA NIEDRINGHAUS | Associated Press   After losing the match, Amelie Mauresmo walked off Centre Court without acknowledging the crowd. ANJA NIEDRINGHAUS | Associated Press

Mauresmo, who won her first two Grand Slam titles last year, had 14 double-faults and 37 unforced errors.

"I don't know how many I had today, but definitely too many," Mauresmo said. "I don't know if it was her or me."

The fourth-seeded Mauresmo held three set points when she led 6-3 in the tiebreaker but then lost the next five points. After winning the second set, she fell behind 3-0 in the third and was broken again in the sixth game, allowing the 18-year-old Vaidisova to serve out the match.

Vaidisova will play No. 6 Ana Ivanovic in the quarterfinals. The Serb held on to beat Nadia Petrova 6-1, 2-6, 6-4 in a match interrupted by rain four times.

No. 3 Jelena Jankovic also was upset, losing to No. 18 Marion Bartoli of France 3-6, 7-5, 6-3. Bartoli will face No. 31 Michaella Krajicek in her first Grand Slam quarterfinal.

Also, 2004 U.S. Open champion Svetlana Kuznetsova reached the quarterfinals by beating 16-year-old Tamira Paszek of Austria 6-3, 6-2.

"I put in more and more pressure on her," Kuznetsova said. "She was playing worse, worse, worse."

Kuznetsova will face either Venus Williams or Maria Sharapova in the next round. Williams and Sharapova were scheduled to play later today.

On the men's side, 2003 French Open champion Juan Carlos Ferrero reached the Wimbledon quarterfinals for the first time by beating Janko Tipsarevic 7-5, 6-3, 7-6 (5).

Mauresmo double-faulted twice in the sixth game of the final set to give Vaidisova a break point. She then sent a backhand drop shot into the net, and netted a volley on the first point of the next game.

She then hit a ball into the crowd in frustration and was given a warning by the umpire. After the match, Mauresmo walked off Centre Court without acknowledging the crowd.

Mauresmo was sidelined earlier this year following an appendectomy in March and had a groin problem that contributed to an early exit at the French Open.

"Sometimes it shows that it's a lack of confidence and a lack of practice," Mauresmo said. "I just want to come back to the level I had quickly."

Vaidisova reached the quarterfinals for the first time at the All England Club. The No. 14-seeded Czech reached the semifinals at last year's French Open and this year's Australian Open.

"She's got some maturity on the court. She's showing she can go for shots at the right time," Mauresmo said. "She's been close already."

Play was twice delayed early in the match, each time for about 20 minutes. The third delay came when Mauresmo was about to serve for the second set, and lasted nearly an hour.

This year's tournament has been hampered by rain in seven of its first eight days.