Microsoft says it has restored its instant messaging service to most of the 10 million users shut out of the system by a glitch but said some were still having problems.
"Most customers should be able to access Messenger but they are still working to restore the service worldwide," a Microsoft spokesman said.
Some MSN Messenger users reported trouble logging in and accessing their "buddy lists" of identified friends on the system early last week.
At its peak, Microsoft said the outage affected about a third of the more than 30 million users of its service around the world.
As of this morning, Microsoft estimates about 10 per cent of users were still having troubles, although the company had no further details about the disruption.
The service, which allows users to send and receive short text messages in real time, was taken down by what the Microsoft spokesman called "a rare set of hardware failures".
The nearly week-long outage has been the most severe for Microsoft since January, when a series of technical errors and a hacker attack shut down parts of its Internet offerings, including its popular, free e-mail service Hotmail.
The continuing service problem with the MSN Messenger Service is an embarrassment for Microsoft as it pushes a new strategy for fee-based Internet services, some of which will rely on its instant messaging capabilities.
Since Friday, Microsoft has been posting periodic updates on progress in restoring the messenger service on its website, at http://messenger.msn.com/support/helphome.asp.