Third seed Lleyton Hewitt claimed a four-set win over Argentina's Juan Ignacio Chela in an ill-tempered clash.
Tension rose in the last set when Chela became irritated by Hewitt's trademark shouts, and he appeared to spit towards the Australian at a change of ends.
Chela also seemed to drive a ball straight at Hewitt, but he eventually prevailed 6-2 4-6 6-1 6-4 to set up a fourth-round clash with Rafael Nadal.
The Spanish teenager earlier beat US qualifier Bobby Reynolds 6-1 6-1 6-3.
Hewitt and Chela shook hands at the end of their match and the Australian said he had accepted his opponent's apology.
"He spat in my direction. He apologised to me at the net after the match and I accepted his apology," said Hewitt.
"It's unfortunate because we were having a good dogfight.
"It's sad something like that happens but at the end of the day he apologised and I said just 'Forget about it mate'."
Chela admitted spitting, but denied it was in Hewitt's direction.
"Lleyton thought it was at him and I apologised for that at the end of the match. But I was not spitting at Lleyton," Chela said through an interpreter.
Andy Roddick powered past Austria's Jurgen Melzer to seal a spot in the fourth round.
The American, seeded two, needed just one hour and 35 minutes to claim a 6-2 6-2 7-5 victory.
It was another immaculate performance from Roddick, who followed up his total of eight unforced errors in four sets against Rusedski with just another 12.
Roddick, who hit 41 clean winners and broke Melzer five times, now faces Germany's Philipp Kohlschreiber.
"I thought I played maybe better in the second and third sets than I did in the first set," Roddick said after his victory.
And he is looking to maintain his blistering form against the unheralded Kohlschreiber.
"I played him in St Polten in 2003 and he's pretty aggressive from the baseline," the American added.
"He's not super big, but he can hit great shots and then go away sometimes. My goal is just going to try to be to play solid."
Guillermo Coria made light work of seeing off Juan Carlos Ferrero.
The Argentine booked his place in the fourth round with a 6-3 6-2 6-1 win over the Spaniard, a semi-finalist at Melbourne Park 12 months ago.
Ferrero, who has struggled since, started brightly breaking the sixth seed in the opening game.
But Coria bounced back immediately and controlled the match with increasing confidence breaking serve seven times.
"I felt excellent," Coria said. "I made the most of the moments where I could break his service and I feel really confident for the next match."
Coria will play compatriot David Nalbandian next after the ninth seed beat Chile's Fernando Gonzalez in four sets.
The 2002 Wimbledon finalist converted a third of his 24 break point chances to win 6-7 (3/7) 7-5 6-2 6-3.
Guillermo Canas, a third Argentine, breezed past Radek Stepanek of the Czech Republic 6-1 6-2 6-2.
Canas will play Tim Henman's conqueror Nikolay Davydenko in the fourth round.