Microsoft\u2019s highly anticipated upgrade of its MSN Spaces blogging and social networking service has run into significant and unforeseen performance problems.Microsoft began rolling out the "next generation" version of the service, dubbed Windows Live Spaces, on Tuesday night, but things got quite bumpy along the way.For more than 12 hours, pages loaded extremely slowly at best, and at worst they didn\u2019t render properly at all, according to a message posted late Wednesday by Microsoft on the official MSN Spaces blog."We know we disappointed a bunch of you with the issues we had in our rollout last night," the message reads. "We planned long and hard for this release and unfortunately it was one of those gotchas that only showed up once we were in production."Microsoft has been working hard to fix the problems and has solved some of them, according to the posting. Still, in angry comments to the posting, exasperated users continue to report a variety of design and performance problems. A common request from them is for Microsoft to roll back the upgrade until all the problems are taken care of.Microsoft didn\u2019t immediately respond to a request for comment.MSN Spaces is one of the most successful online services launched by Microsoft in recent years, and its popularity has been a great source of pride for the company, which is otherwise fighting a losing battle against Google in the search engine market.About 40 million people have set up MSN Spaces blogs, and the network receives about 120 million unique users per month, Karin Muskopf, an MSN product manager, said in June.The Windows Live Spaces upgrade gives the service an extended social-networking functionality that is a clear attempt to provide features made popular by News Corp.\u2019s MySpace. The upgrade is also designed to make it easier for people to customize their blogs through support for Microsoft Gadgets. These are lightweight applications that can extend the functionality of larger desktop and Web-based applications.By Juan Carlos Perez, IDG News Service (Miami Bureau)This article is posted on our Microsoft Informer page. For more news on the Redmond, Wash.-based powerhouse, keep checking in.Check out our CIO News Alerts and Tech Informer pages for more updated news coverage.