Former triple champion Venus won the last four games of her third round clash with Akiko Morigami of Japan to move into the fourth round with a 6-2, 3-6, 7-5 win.
But just a few hours later, she watched as sister Serena, the 2002 and 2003 champion, saw her hope of making the quarter-finals – and a date with top seed Justine Henin – left hanging by a thread by a painful left calf injury.
Serena was leading Slovakia's Daniela Hantuchova 6-2, 5-5 when she collapsed in front of the Royal Box, clutching her left leg and needed a three-minute injury time-out.
The Slovakian won the second set tiebreak but the American seventh seed, now with her leg strapped and reduced to walking pace, was handed a reprieve when play was suspended for a second time because of rain allowing her time to get treatment.
On Court Two, Venus was helped into the last 16 by Morigami who converted just four of 23 break points and had the chance to serve out the match in the eighth game of the final set in a tie which had been suspended from Saturday because of the rain.By the time the 23rd seeded Williams had wrapped up her third round encounter, Henin was already back in the locker room having secured her quarter-final place by brushing aside Switzerland's Patty Schnyder 6-2, 6-2.
Austria's 16-year-old Tamira Paszek shocked Russian 12th seed Elena Dementieva, a quarter-finalist last year, 3-6, 6-2, 6-3, to reach the fourth round on her Wimbledon debut.
The teenager had lost the first set when play was halted on Saturday.
Paszek, coached by Larri Passos who took Gustavo Kuerten to three French Open titles, now faces former US Open winner Svetlana Kuznetsova for a place in the last eight.
Fifth seed Kuznetsova saw off Agnieszka Radwanska of Poland 6-2, 6-3 and Czech 14th seed Nicole Vaidisova defeated Victoria Azarenka of Belarus 6-4, 6-2.
Vaidisova meets defending champion Amelie Mauresmo for a quarter-final spot while Russian 11th seed Nadia Petrova, who saw off Spain's Virginia Ruano-Pascual 6-3, 7-6 (7-3), goes on to face French Open finalist Ana Ivanovic.
The Serbian sixth seed made sure of her place in the last 16 by beating Aravane Rezai of France 6-3, 6-2.
Later on Monday, if the rain relents, Serbian third seed Jelena Jankovic faces France's Marion Bartoli in the fourth round with the winner to face either Michaella Krajicek or Laura Granville for a semi-final place.
On the men’s side, Roger Federer was able to put his feet up, kick back and enjoy the sight of his rivals suffer as rain once again played havoc with the playing schedule at the All England Club.
Having got his own third round match out of the way by beating Marat Safin in quickfire fashion on Friday evening, Federer was handed a bye into the quarter-finals when German No 1 Tommy Haas pulled out of the tournament with a torn stomach muscle, and will not play again before Wednesday.
The contrast with the frustration endured by the principal pretender to Federer's crown, Rafael Nadal, could hardly have been greater.
The French Open champion, who had only been able to warm up for his third round match against Swedish No 1 Robin Soderling on Saturday, was forced to retreat to the locker room no fewer than three times on Monday – the third interruption coming with him leading by two sets and having just failed to convert a match point at 7-6 in the third set tie-break.
Although he was close to victory, Nadal's performance had not been totally convincing and he had reason to be grateful to Soderling's tendency to implode at key moments.
Either Jarkko Nieminen of Finland or Russia's Mikhail Youzhny awaits the winner in a fourth round.
In one of only two men's matches to be finished by 1700 GMT, former finalist David Nalbandian slumped to a 6-2, 7-5, 6-0 defeat at the hands of Cypriot Marcos Baghdatis.
Former Australian Open runner-up Baghdatis will face either Nikolay Davydenko or France's Gael Montfils for a place in the last eight.
Seventh-seeded Tomas Berdych, who had been a set up when his third round match was interrupted by rain on Saturday, had earlier finished off South Korean number one Lee Hyung-Taik 6-4, 7-6, (7-2), 7-6 (7-3).
Meanwhile, security was stepped up around Wimbledon in the wake of the attempted car bomb attacks in Glasgow and London with even the players unable to drive into the grounds.
A police helicopter hovered above the venue in south-west London while all entrances were protected by a series of vehicle-blocking concrete slabs to foil similar attacks.
Monday’s results (prefix number denotes seeding):
Men’s singles:
Fourth round: 1-Roger Federer (Switzerland) beat 13-Tommy Haas (Germany) – walkover.
Third round: 10-Marcos Baghdatis (Cyprus) beat 23-David Nalbandian (Argentina) 6-2, 7-5, 6-0; 7-Tomas Berdych (Czech Republic) beat Lee Hyung-Taik (South Korea) 6-4, 7-6 (7-2), 7-6 (7-3).
Women’s singles:
Fourth round: 1-Justine Henin (Belgium) beat 15-Patty Schnyder (Switzerland) 6-2, 6-2.
Third round: 23-Venus Williams (US) beat Akiko Morigami (Japan) 6-2, 3-6, 7-5; Tamira Paszek (Austria) beat 12-Elena Dementieva (Russia) 3-6, 6-2, 6-3; 11-Nadia Petrova (Russia) beat Virginia Ruano Pascual (Spain) 6-3, 7-6 (7-3); 6-Ana Ivanovic (Serbia) beat Aravane Rezai (France) 6-3, 6-2; 5-Svetlana Kuznetsova (Russia) beat Agnieszka Radwanska (Poland) 6-2, 6-3; 14-Nicole Vaidisova (Czech Republic) beat Victoria Azarenka (Belarus) 6-4, 6-2.—Agencies