Google renamed and upgraded its personalized homepage this week, but one thing the update couldn't shake was a bug that began upsetting many users last Thursday and persisted until Wednesday.

The bug caused the free service, which lets users turn Google.com into a customized portal, to revert an undetermined number of pages to their default settings or to months-old versions.

The problem rattled users who spend significant time and effort tailoring their Google.com page with syndicated content feeds, as well as with "gadget" applications, to make it their hub for web content, online services and applications.

A source familiar with the issue said the bug affected "a single digit percentage" of users of this service, which company officials have said has "tens of millions" of users. This means that the number of affected users could range from a minimum of 200,000 to several million.

Discussion forums erupted last Thursday morning with reports from upset users, and Google, after acknowledging the problem, didn't declare it fixed until almost 36 hours later.

However, over the weekend, reports kept flowing into discussion forums of users saying the fix hadn't reached their pages, and continued throughout Monday, even as Google's Marissa Mayer, vice president of search products and user experience, hosted journalists in the company's headquarters to unveil the improvements to the service, now called iGoogle.

On Tuesday morning, as the volume of complaints in discussion forums increased significantly, with a new wave users reporting the problem for the first time, it became apparent that the bug had cropped up again and was affecting an entirely different batch of iGoogle pages.

The problem is now solved, according to a Google spokeswoman. "A number of Google users had difficulty accessing their settings and preferences on their iGoogle pages over the past day," she said. "Users should have their iGoogle pages restored at this time."

A Google official who posts under the name Google Guide Jaime in an online discussion forum gave his most recent update on Tuesday, acknowledging the resurgence of the bug at that time. "We've been keeping a close eye on this thread and are continuing to investigate the remaining missing homepages as well as the recent reports from those who've just lost your homepages in the past few hours," the official said.

In declaring the problem solved last week, Google declined to explain what caused it or how many people were affected, saying only that the bug had been an "isolated incident" and that it had hit "a relatively small group of users." Wednesday, the spokeswoman also declined to provide these details.