Ana Ivanovic overcame her toughest test so far, prevailing against Russia's Nadia Petrova to book her place in the quarter-finals.
The 19-year-old Serb cruised to victory in the first set, but a short rain break revitalised 11th-seeded Petrova, who claimed the second before Ivanovic hit back in the decider to secure a 6-1 2-6 6-4 triumph.
The number six seed now faces Amelie Mauresmo's conqueror, Nicole Vaidisova, for a place in the semi-finals.
Vaidisova was forced to endure three rain breaks before disposing of an out-of-touch Mauresmo, the defending champion, while Marion Bartoli, of France, caused the second shock of the day by fighting back from a set down to oust third seed Jelena Jankovic.
The 18th seed booked a quarter-final date with Dutch teenager Michaella Krajicek, who put out Laura Granville, of the United States.
Fifth seed Svetlana Kuznetsova ended the fairytale hopes of 16-year-old Austrian Tamira Paszek with a straight-sets win.
Womens Singles 4th rd:
(5) Svetlana Kuznetsova (Rus) bt Tamira Paszek (Aut) 6-3 6-2, (18) Marion Bartoli (Fra) bt (3) Jelena Jankovic (Ser) 3-6 7-5 6-3, (14) Nicole Vaidisova (Cze) bt (4) Amelie Mauresmo (Fra) 7-6 (8-6) 4-6 6-1, (6) Ana Ivanovic (Ser) bt (11) Nadia Petrova (Rus) 6-1 2-6 6-4.
