Google mistakenly disabled the Gmail accounts of an undetermined number of users due to an apparently overzealous attempt by the company to combat spammers.
People started reporting in the official Gmail Help Discussion forum last Wednesday that Google had locked them out of their accounts.
A Google staffer who patrols the forum and posts messages on behalf of the company acknowledged the existence of a problem on Thursday.
"I understand that some of you have had a frustrating experience with your accounts being inappropriately disabled. Our team is aware of the problem, and our engineers are continuing to investigate," this person, identified as Google Guide, wrote.
In a subsequent post to the forum, Google Guide provided more details about the situation, saying that it was the result of an effort to purge users who abuse the service, such as spammers.
People whose accounts were disabled by mistake should have regained access to them already and no data should have been lost, the Google staffer wrote.
However, it seems that Gmail declined accepting messages sent to those accounts while they were disabled, informing senders with a 'bounce-back' return notice. It's not clear if Gmail will automatically attempt to redeliver those rejected incoming messages.
Also, as recently as late Friday morning some people were still complaining of being locked out of their accounts.
Google didn't immediately reply to a request for comment.
Although the extent and scope of the problem is unclear, the discussion thread is at press time one of the longest in recent months, and is full of frantic pleas for help from affected people who use Gmail as their primary e-mail service for personal or work communications.
In addition to the problem of disabled accounts, in the past month a steady stream of Gmail users have been complaining that when they get upgraded to the new version of the service, popularly called Gmail 2.0, the service becomes extremely slow, often fails to load pages and even crashes their browsers.
One of several threads devoted to this issue in the Gmail Help Discussion forum continues growing, nearing 300 messages at press time.
Gmail 2.0, which features an upgraded contacts manager and is designed to be faster and more stable, is based on what the company calls "a major structural code change".
Gmail isn't just a free webmail service for individuals, but also part of the company's Google Apps suite of hosted collaboration and communication applications suite, which is used by more than 100,000 organisations, mostly small businesses, as well as by hundreds of universities.
Google offers a service-level agreement of 99.9 percent uptime to people and organisations that sign up for the Premier edition of Google Apps, which costs $50 (£25) per user per year.