"We have taken the service offline to deal with the issue," Microsoft product manager Laura Norman said in a statement. "We are working with our partners to repair the system at this time, and I cannot provide a time frame for restoring the service.
"We offer our deepest apologies to members for the inconvenience, and please know that we are working 24x7 to restore service as quickly as possible," she added.
One user, while acknowledging that Jump is still only in beta, said that getting locked out of his online calendar gave him doubts about whether to trust such a service in the future.
"I'm an attorney who depends heavily on the accuracy and accessibility of my calendar," said the user, who asked not to be identified, in an email to News.com. "This experience has deterred me from moving to a Web calendar service...and makes me question whether I could (reliably) use a Web calendar service to post...events for my clients/co-workers to review."
Microsoft's purchase of Jump Networks came as more and more computer applications have been shifting from the desktop to Web portals. Online calendars are seen by many as the second big wave of free, Web-based portal utilities, following free email. America Online in April acquired online calendar service When.com.
Microsoft has a history of service problems with another portal service acquisition, MSN Hotmail. Users have persistently complained of outages and overloads at the Web-based free email provider as subscriber rolls have swelled to more than 40 million.