The outage also brought down for a while MSNBC.com and Newsweek.com, which has a hosting arrangement with the Microsoft-NBC news site.
Sunday's lack of access was the latest in a series of recent glitches affecting MSN Web sites or Passport online authentication services.
Users could not access Microsoft's popular Game Zone Web site, nor could they log in to popular MSN chat rooms. Some Hotmail users also found they could not access the Passport log-in page. The outage also affected Internet Explorer 6 users, who discovered they could not search the Web using the default setting. IE 6, which is integrated into Windows XP, uses MSN for Web searches.
"This also affected people wishing to sign out of their Passports on the Zone.msn.com site, causing a potential security issue for that segment of their Passport access," said Shane Johnson, a network/messaging consultant from Puyallup, Wash.
Not being able to log out could be as much of a problem as not being able to log in. Users typically need to sign out of Microsoft services such as bCentral, Game Zone and Hotmail, all of which requireauthentication, to avoid exposure to a possible security problem. The action removes a cookie that, if pilfered by a Web site or other program, could allow a hacker to take control of the account.
CNET News.com started receiving user complaints about the outage around 9:15 a.m PDT Sunday and later confirmed through testing that some kind of failure had occurred with a number of MSN Web sites or services. Most services appeared to have been restored early Sunday afternoon.
Johnson was one of those users alerting CNET News.com to the problem. He concluded that Microsoft had a problem with one of its primary backbone routers.
Microsoft could not be reached for comment about the problems.
Microsoft's .Net Messenger service appeared unaffected by the outage, as were the main MSN and Microsoft Web sites.
Sunday's outage follows a string of gaffes or security glitches that have called Microsoft's .Net Web servicesinto . In court last week, testifying as part of Microsoft's antitrust trial, Jim Allchin, the company's senior vice president responsible for Windows, .Net My Services as being "in a little bit of disarray."
In April, a server glitchmany Hotmail users out of their accounts. In January, a glitch with Passport authentication some users from accessing Microsoft's game site. This followed a more serious December , when Microsoft's switching users over to Passport authentication prevented some users from logging onto the Web site.
On Wednesday, Microsoftof a critical security hole in MSN Messenger's chat feature. In February, a fast-spreading worm a glitch in MSN Messenger, while another problem some and MSN Messenger users from staying connected to the Internet. A summer 2001 kept about 10 million Messenger users offline for about a week.
Instant messaging is an important component of Microsoft's .Net My Services, the company's consumer Web services offering that is under construction. Microsoft plans to use Windows Messenger, which is integrated into Windows XP, and MSN Messenger as a way for the company and third-party service providers to communicate with customers. The first such service,, delivers stock quotes, traffic reports and other information through Microsoft's instant messenger.
Other security problems continue, despite Microsoft Chairman Bill Gates' call earlier this year that the company put moreon making software secure than adding new features.
In March, Microsofta pair of patches for Internet Explorer security holes. and security holes potentially opened Office for the Mac to hackers. Also in April, Microsoft fixes for about 10 security holes affecting three versions of Internet Information Server.