Defending Olympic champions Yang Wei and Zhang Jiewen were dumped out of the quarter-finals of the women's badminton doubles in front of their home crowd.
The Chinese pair had been two points from victory, but Japanese duo Miyuki Maeda and Satoko Suetsuna fought back to win the match 19-16 23-21 14-21.
Defending men's singles champion Taufik Hidayat also crashed out, losing to Malaysia's Wong Choong Hann.
British pair Tracy Hallam and Andrew Smith were also eliminated.
Hallam lost 21-10 21-7 in the last 16 of the women's competition to Germany's seventh seed Huaiwen Xu, while Smith fell to Marc Zwiebler 16-21 21-13 21-17 in the last 32.
Yang and Zhang's defeat stunned the buoyant crowd at the University of Technology Gymnasium.
The top seeds had been 19-16 ahead in the second game, but a series errors allowed their opponents to take the match into a third game.
"This was the biggest win of our lives," said Suetsuna. "They are the Olympic champions so even when we had 20 points in the third game we couldn't take anything for granted.
"It wasn't until we got that final point that we could celebrate."
There were no such concerns for compatriots and second seeds Du Jing and Yu Yang, who crushed Japan's Kimuko Ogura and Reiko Shiota 21-8 21-5.
Men's singles seventh seed Hidayat, who had been discharged from hospital two weeks ago after suffering with dengue fever, was beaten 21-19 21-16 in what could be his last appearance at the Olympics.
"My condition is not 100%, but today it was really good play from him," said the Athens gold medal winner. "Waiting four years, when I'm 31 or 32, it's too old for me."
China's top seed Lin Dan moved into the last 16 courtesy of a 21-16 21-13 win over Hong Kong's Wei Ng.
There were also wins for fourth seeded Chen Jin, sixth seed Sony Dwi Kuncoro of Indonesia and eighth seed Peter Gade of Denmark.
Hallam's hopes of reaching the quarter-finals of the women's singles ended thanks to a comprehensive display from her Chinese-born opponent.
There were also wins for China's defending champion Zhang Ning, while compatriots Chen Jin and Xie Xingfang also advanced into the last eight.
~RS~q~RS~~RS~z~RS~29~RS~)