If you've got a working Gmail account, you might want to back it up every so often -- as many as 500,000 Gmail users lost access to their inboxes this morn, and some of them are reporting (via Twitter and support forums) that years worth of messages, attachments and Google Chat logs had vanished by the time they were finally able to log on. While we haven't experienced the issue personally, we're hearing that the bug effectively reset some accounts, treating their owners as new users complete with welcome messages. For its part, Google says that the issue "affects less than .29% of the Google Mail userbase," engineers are working to fix the issue right now, and that missing messages will be restored as soon as possible. We'll soon see if this is a momentary setback... or a lengthy wakeup call.

Update: No fix yet, but Google's revised its estimate as to how many users might have been affected by the issue -- "less than 0.08%" -- which means we're probably looking at closer to 150,000 individuals, rather than 500,000. We're assuming that the revised estimate means that the initial count wasn't precise, and not that customers are ditching Gmail in droves.

Update 2: Google's provided promising but terribly vague guidance on when the situation will be resolved: "Google Mail service has already been restored for some users, and we expect a resolution for all users in the near future. Please note this time frame is an estimate and may change."

Update 3: One-third of users have now had their account access restored, according to Google. Read all about it here.

[Thanks to everyone who sent this in]