Top seed Justine Henin-Hardenne was put through her paces by French qualifier Camille Pin, but still advanced safely to the third round.
The Belgian won 6-1 6-4 in 66 minutes against Pin, a childhood friend, who managed one break of serve.
Despite the emphatic scoreline, it was far from Henin-Hardenne's best form, who made 23 unforced errors.
"I haven't felt well for two or three days and I was feeling a little bit tired," said Henin-Hardenne.
"I wasn't feeling great out on the court. I need some rest for
sure," she added.
The world number one is likely to have to improve when she faces Svetlana Kuznetsova in the next round.
Kuznetsnova, the 30th seed, also produced a patchy display, but did enough to see off Antonella Serra Zanetti 7-6 (7/0) 6-4.
Fifth seed Lindsay Davenport did not have it all her own way against Emilie Loit of France.
Davenport took the first set 6-3 but Loit levelled the match after taking the second by the same score.
However the American upped her game and steamed through the third set without losing a game.
The Russian, who reached the last eight at Wimbledon last year, hit 43 winners but also made 44 unforced errors.
Hungary's Petra Mandula came back from a set down to knock out Bulgaria's 24th seed Magdalena Maleeva.
Mandula, ranked 39, made most of the running with 44 winners to 28 but also made more mistakes.
Maleeva had plenty of chances to win but squandered a string of break points and dropped serve an incredible 10 times in the match.
Mandula's prize for the 6-7 (6/8) 6-2 6-3 win is a third-round match against Hungary's Aniko Kapros.
Greek 19th seed Eleni Daniilidou also came from behind, beating Zimbabwe's Cara Black 3-6 6-0 6-1.
But 21st seed Elena Bovina was another casualty as she was beaten by Claudine Schaul of Luxembourg.
Schaul beat her seeded opponent 6-4 6-3 and earns a third-round match against Alicia Molik or 15th seed Daniela Hantuchova.