The problem, which affected services including Yahoo Mail and My Yahoo, lasted less than an hour, according to Yahoo and Web site performance measurement company Matrix NetSystems.
"For a brief period today of approximately 45 minutes, certain areas of Yahoo were inaccessible to a portion of users due to software-related issues," a Yahoo representative wrote in an e-mail statement.
"We have identified the issue, and corrected it," the representative continued. "We know that this may have caused some inconvenience, and we apologize to Yahoo users who might have been affected. We take these issues extremely seriously, and Yahoo is instituting new processes to protect against similar incidents from occurring again."
Tuesday's outage comes just two weeks after Yahoo fixed athat shut down communication lines for millions of members using the portal's Yahoo Groups e-mail list service.
Yahoo is in the process of merging its Yahoo Groups and Yahoo Clubs, a similar Web-based community that uses online posting and instant chat to communicate. Yahoo started integrating the services about four weeks ago and plans to have the project finished by the end of March.