The most recent outage occurred Friday morning, when Pacific Bell crews performing routine maintenance "inadvertently caused a routing problem," a PacBell representative said.
Technicians had patched up the problem by 9:15 a.m., about two hours after it was discovered, the spokesman said.
A utility spokesman said some of Pacific Bell's 400,000 Internet customers had limited access to the Web and were only able to reach a handful of sites. Although he couldn't estimate the number of customers affected, he said the problem was confined to the San Francisco Bay Area.
On Thursday afternoon, a hardware problem at AT&T, which helps to support PacBell's Internet service, caused the system to crash about 3:15 p.m. Repairs were made within an hour. The cause of the problem is still under investigation, according to AT&T spokesman Bill Hoffman.
Hoffman couldn't estimate how many users were affected but said there were only a minimum number of calls for service.
"We deeply regret any inconvenience caused to our customers," he added.
Hoffman said it was the first time that particular router had crashed in the years that AT&T has been offering Internet service.
Pac Bell has experienced a number of problems in its Web services division, however. Earlier this month, a San Diego customer filed a lawsuit claiming the company made him wait eight hours for a DSL installation. California law limits the wait to four hours, the lawsuit claims.
PacBell also had problems with its billing and customer service departments earlier this year. Subcontractors signing up customers for DSL service were forced to file work orders on paper because of a customer service snafu, sources said at the time.