Google's Personalized Home Page service, which lets users turn into a customised portal, is suffering from an apparently significant technical problem that’s reverting some of the home pages to old versions or to their original default settings.

Angry users lit up discussion boards on Thursday, complaining about the problem and expressing frustration at the possibility that they have lost the time they spent customising their pages, while lamenting the hit on productivity the issue has caused them.

"I had four tabs stuffed with content on my personalised homepage. Dozens of RSS feeds, half a dozen bookmark gadgets, friends blogs, all my web presences, dozens of other gadgets. I spent weeks tailoring [it] so it was just right for my very intensive internet needs," a user wrote on a Google discussion group. "Now it's all gone."

The problem apparently affects a portion of Personalized Home Page users. It's not clear how many or why. Google didn't immediately respond to a request for comment.

A Google official posting to one of the longer threads about the problem wrote in a message that Google is in "frantic-chase-down-this-bug mode here at the Googleplex, and I hope to have more info for you soon”.

The official, posting under the name Google Guide Jaime, acknowledged that Google engineers are in the dark about the cause of the problem.

"It's possible that changing your homepage theme might cause the problem. So, if you still have your homepage intact, please avoid changing your theme until further notice," he wrote.

Alarmingly, he also acknowledged it's not clear whether users will be able to recover their customised pages.

The problem is the latest in what seems a regular stream of technical glitches and availability problems affecting Google's online services. In the past six months, Google services like Blogger, Gmail and Google Apps have all experienced significant technical issues that have left users fuming.

The problems highlight one of the risks of relying on hosted applications providers, which offer to house software and its data for individuals and organisations. Google is one of the biggest cheerleaders for this software provisioning model, which many see as a viable option to the traditional approach of having users install applications on their own PCs and servers.

Personalized Home Page is a free service that lets users add information and "gadget" applications to and thus create their own web entry page hosted by Google. Users can display in their home page news story headlines, weather information, RSS feeds, as well as hosted applications from Google and other providers, like Gmail and Yahoo's Yahoo Mail. That way, Personalized Home Page can be tailored as a hub for a user's web content, services and applications.