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Wayne Ferreira felt he had been "screwed" by a controversial overrule during his third round defeat by Britain's Tim Henman at Wimbledon.

Ferreira demanded an apology from Portuguese umpire Jorge Dias over the crucial decision in the third set tie-break in Henman's 7-6 3-6 7-6 6-1 victory on Centre Court.

The South African was leading 4-1 when his forehand passing shot was called in by the line judges but then overruled by Dias, even though it was on the far side of the court from his chair.

Television replays indicated the ball had clipped the line but instead of leading 5-1, Ferreira was pegged back to 4-2, and went on to lose it 10-8 in an obvious turning point of the match.

"I think it's shocking. If he had any decency I think he would at least come and apologise," said Ferreira. "He ummed and aahed about it being close, touching the side, but maybe long.

"He wasn't really sure. It was a total intimidation thing. I think he realised he made a mistake but what can you do about it?"

Henman's initial reaction was that the disputed overrule from the umpire was correct, but felt he had not intimidated Dias into making a decision.

"I've not seen it on television, my gut reaction said it was out but I'm sure that had a lot of hope to it," said the fourth seed, who now faces Switzerland's Michel Kratochvil in the fourth round on Monday. "If television says it was in Wayne has every right to feel disappointed.

Henman knows he will have to play better to become the first British winner for 66 years however, especially if he goes on to face world number one and top seed Lleyton Hewitt in the semi-finals.

Britain's only remaining player in the ladies' singles, Elena Baltacha, made her Wimbledon exit on Saturday.

The teenager was beaten 6-4 7-6 by Russian Elena Likhovtseva.

A poor early service game from the Briton proved decisive in the opening set, but she fought back well and moved 4-1 ahead in the second.

But she failed to secure a second break of serve and when her opponent broke back, a tie-break ensued which Likhovtseva took 7-2.

Baltacha will leave Wimbledon with a cheque for £17,000 - her next stop is a Challenger tournament in Felixstowe.

She said: "I've had a brilliant time this week and it's given me a great boost for the future.

"I've learned a lot of things. I kept fighting and I kept digging in. But I know there are still lots and lots of things to improve on."

After coming to Wimbledon with a wild card in her pocket and a singles ranking outside the top 300, she can now expect a top 200 berth and with it qualification for the qualifying rounds of this year's US Open.

Her coach Alan Jones said: "Elena can walk away knowing that she was in the match today.

"Winning this one would have been the icing on the cake but it's a learning curve. What she's achieved here has already caused us to rethink her schedule."

Meanwhile, defending champion Venus Williams ran into a real battle and had to come from behind to reach the last 16.

Williams was rocked by 110-ranked Canadian Maureen Drake and was broken four times in the match before triumphing 5-7 6-2 6-1.

She was broken to love in the very first game and a huge shock looked on when Drake took the first set.

But Williams, suffering from tendinitis in her knee, found a new level after that and surged on to win.

Monica Seles, the fourth seed, fought back after losing the first set to defeat Ai Sugiyama and reach the last 16.

The American lost a tight first set 6-4, but that seemed to jolt her into action.

Seles hit back by taking the second 6-1 to level the match and after powering ahead in the decider, she eventually took that 64 to win in an hour and 37 minutes.

Seles, who had dropped only four games in the championships before, admitted she was spurred on by her loss of the first set.

"I got a wake-up call," she said. "It made me play and become more focused.

"I started sluggishly but I played well in the second set and the third set. I have come close to losing a set to her in the past and this surfaces suits her game the most."

Seles next faces Thailand's Tamarine Tanasugarn after she beat Melien Tu.

Meanwhile, tenth seed Silvia Farina-Elia made her exit, losing in straight sets to Magdalena Maleeva.

The Italian dropped the first set on a tie-break to 19th seed Maleeva, seven points to two.

And although Maleeva struggled to see the match out, squandering a 5-1 lead, she eventually survived more break points in the tenth game to win 7-6 6-4.

Lisa Raymond accounted for former champion Conchita Martinez in the third round.

Grasscourt specialist Raymond, seeded 16 this year, set up a likely meeting with the reigning champion Venus Williams with a 2-6 6-3 6-2 win.

Elena Dementieva continued her smooth progress through the draw.

The 12th seeded Russian beat former French Open champion Iva Majoli 7-5 6-2 to reach the last 16.

Dementieva will next face sixth seed Justine Henin, last year's runner-up, who beat 17-year-old Myriam Casanova 6-4 6-4.

Henin said: "I'm happy to be in the fourth round - and that the first week is finally over.

"The victory was the most important thing today but it is hard to play someone you have never seen before and who you don't know anything about. It can be very dangerous.

"She was hitting the ball so hard and there were not many shots in the rallies so it was difficult to settle."

In the men's singles, the seeds continued to fall with Nicolas Escude going out to Mikhail Youzhny.

The 16th seed, who helped France to Davis Cup glory on grass last year, was unable to handle Youzhny's game and went down in four sets, 6-3 1-6 6-2 6-2.

And Rainer Schuettler, the 17th seed, surprisingly crashed out to Spain's Feliciano Lopez.

The Spaniard fought back after dropping the first set 6-3 and the second-set tie-break proved crucial.

It went to Lopez by nine points to seven, and proved a turning point in the match.

The next two both went to Wimbledon debutant Lopez 6-4 as he booked his place in the last 16.

But the last singles match of the day went as expected with top seed Lleyton Hewitt racing to a straight-sets win over Julian Knowle.

The impressive Hewitt romped to a 6-2 6-1 6-3 victory and has yet to drop a set in the tournament.