Sharapova committed two consecutive double-faults to drop her serve at the start of the decisive set.
Sharapova had 57 unforced errors, including 13 double-faults, and overcame three set points in the second set.
The Serbian made 40 unforced errors and served four double-faults as she lost to Bondarenko for the first time in 10 meetings.
All told, Sharapova benefited from eight double-faults by the No. 29-seeded Vesnina, and erased eight of the nine break points she faced.
The Russian made 30 unforced errors, three double-faults and hit only won clean winner as she lost in 91 minutes to the unseeded 31-year-old.
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Venus struggled with her serve in the first set, making five double-faults, but still won it easily as both players went for their shots.
Seeded third, Azarenka hit 10 double-faults and was broken six times.
Serve was again key with the Thai player hitting four aces and just one double-fault while the German had just one ace and five double-faults.
She overcame eight double-faults, the erroneous ruling and a second-set deficit to beat Zheng Jie 6-1, 7-5 in the third round Saturday at the French Open.
Two aces by Djokovic and two double-faults by Davydenko helped to decide the first set tie-break only for the match to be turned on its head completely in the second set as Djokovic crumbled.
The crowd were willing Williams on but sadly her inconsistency proved decisive in the next game, as two big serves were followed by two double-faults and a wide forehand that allowed the world number four to close out a dramatic victory.
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Stosur, who had nine double-faults and 56 unforced errors, has never gone beyond the fourth round at her home Grand Slam, lost in the first round last year and also lost in her first matches at warm-up tournaments this year in Brisbane and Sydney.
It is the second time in as many tournaments that Dimitrov has cracked when serving for a set against a top-ranked player, having served four double faults when leading world No. 1 Novak Djokovic 5-3 at Indian Wells earlier this month.
The 21-year-old had the chance to win the first set when serving at 5-3 but three double faults handed the Scot a lifeline.
Hewitt, without a title since his Wimbledon win, took advantage of two double faults to close out the tie-break and the match.
"I just didn't have a spark, " stated the 23-year-old Russian, who served up eight double faults.
Her mood darkened further when Clijsters fashioned an early break in the decider, but at 3-4 the Belgian threw in a couple of double faults of her own before sending a drive volley long.
But, in contrast to last week, the 21-year-old made numerous unforced errors and hit as many double faults as aces.
Dementieva served 19 double faults against Japan's Akiko Morigami but still came through 6-3 4-6 6-3.
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