A major outage to Microsoft Windows Live services has left an unknown number of users unable to access MSN Messenger, Hotmail and other services since earlier today. Progress is being made on resolving the situation, the company says.

Initially believed to be an incident isolated to the east coast of the United States, users from the west coast and several other nations also reported they have been unable to access any Windows Live services since sometime around 6:30 a.m. EST.

Microsoft acknowledged the outage, but did not say how many people were affected or when Windows Live would be fully functional again. Other Microsoft online services such as Xbox Live have also been down for several hours today.

According to the Redmond company, the problem involves Windows Live IDs, which are used to log users into its services. Microsoft says an issue is "purely impacting the log-in process" and those who have already successfully logged in are not impacted.

"We have made significant progress in decreasing the number of customers currently affected since initial reports, but the issue has not yet been completely resolved," Windows Live product manager Samanta McManus told BetaNews. "Microsoft is working quickly and aggressively to resolve the issue and expects to restore normal operation to all customers shortly. Our customers have come to expect a high level of service reliability in their experience with Windows Live and we apologize for any inconvenience this particular issue has caused consumers."

There is a possibility the Windows Live outage issues stem from Microsoft recently upgrading its systems to Windows Server 2008, but Microsoft spokespeople declined to comment on this particular topic. Windows Server 2008 is officially launching tomorrow during an event in Los Angeles with Microsoft Chairman Bill Gates present.

Although many users now say they are able to sign on to Windows Messenger, they still cannot access Hotmail or other Windows Live services.

Windows Live has had issues with downtime in the past, with the last big outage taking place in April of last year. During that incident, users were unable to log in for at least nine hours, and Microsoft declined to officially discuss what caused the problem.