An OptusNet spokesperson told ZDNet Australia delays started Wednesday at 7:30am and blamed a cable break in the United States side of upstream provider Southern Cross' cable network.
However, while she claimed the problem was resolved yesterday by 10pm, Optus customers continued to complain about problems on the forums of broadband information site Whirlpool.
OptusNet's service status Web site lists a "broken fibre" problem which it says ocurred at 8:40am yesterday.
"It will take at minimum three hours to reach the broken fibre," said the Web site. The message was posted at 10:41am.
The spokesperson said she would investigate the matter.