Like the previous two incidents, affected Comcast users experienced slow Web page loading times or could not view pages at all. Comcast said the problems began on Wednesday evening at 5:30 p.m. PDT, and that network access was restored nearly five hours later.
"We're doing everything in our power," said Comcast spokeswoman Jeanne Russo. "We have a team of experts to quickly resolve this issue. We apologize to customers for any inconveniences they are experiencing."
Irate customers, however, vented their frustration about the outages on Comcast's user forums and other message boards.
"The worst thing is that Comcast has kept us in the dark for a week as to why the bills keep coming, but we have no Internet service at all," one CNET News.com reader wrote in an e-mail, referring to the three separate service outages over the past week.
Wednesday's downtime came after a similar three-hour outage on Tuesday and a six-hour blackout last Thursday. All involved issues with the cable giant's domain name servers, which translate and route Web page requests from users. Although Internet applications such as instant messaging could continue to operate, all Web site requests either did not respond or were sluggish.
A Comcast spokeswoman on Wednesday said Tuesday night's outage was first noticed about 6:30 p.m. PDT and service was restored about three hours later.
"We were able to identify the situation right away," Russo said. "We are working with the (hardware) vendor to make sure it doesn't happen again."
Russo on Wednesday said Tuesday night's outage was the result of an issue involving its domain name servers. She declined to identify Comcast's hardware vendor.
Michael Spoonauer, a software engineer and Comcast customer from Quincy, Mass., noticed the issue Tuesday evening when Web site requests continued to time out. He said Comcast's support representative told him the network was experiencing an unscheduled outage due to server maintenance.
Spoonauer bristled at Comcast for not informing its customers about the outage, and added that the company's Web site offered little information about why the service was down again.
"I would consider it to be corporately responsible to send a message to customers saying what happened, why it happened and what they're going to be doing to prevent it," he said. "It's not too much to ask from a company."
Comcast's Russo said the company communicates issues through areas on its Web site and sometimes through recorded messages that greet callers.
Comcast, the nation's largest broadband Internet access provider, reported 7 million subscribers at the end of 2004.