Beware Gmail users: Inserting images into the body of an email message can get you temporarily banned from your account.

The disconcerting bug has been affecting unsuspecting Gmail users for months, and it's apparently tied to the use of Gmail's spanking-new message-compose interface. Google introduced that interface late last year and made it the default for everybody this year, saying it's faster, simpler and altogether better than the old basic HTML interface.

Google has acknowledged the problem but hasn't been able to stamp it out.

The bug is listed in the Gmail Known Issues page and is the focus of several discussion forum threads in Google Groups, including this long one with more than 250 posts.

To reduce the risk of tripping over this issue, Google recommends that people use "a browser other than Firefox" when composing an email with images in its message body.

"I'm scared to continue to rely on Gmail now. I use it for a lot of time-sensitive messages, both personal and for a not-for-profit organization that I work closely with. I cannot afford to be arbitrarily locked out of my account through no fault of my own due to a bug that Google has acknowledged but has left unresolved for months," an affected user wrote in mid-August in a discussion thread, echoing the frustration of many others.

On the Gmail Known Issues page, Google explains that the bug is triggered under certain scenarios involving "inline images" -- images inserted into the body of email messages.

For example, it hits Firefox users who insert images into messages while composing or replying to email. It also strikes users of any browser when they try to do this with large images. Another trigger is to work "over time" on a draft message that contains many images and attachments.

There are no details as to how large an inserted file needs to be to trigger the bug, nor what amount of time is too long when drafting a message with images and attachments.

When the bug is activated, Google locks people out of their account citing "unusual usage" and telling them it has detected "unusually high levels of activity." It can take up to 24 hours for Google to lift the lockout and restore affected users' access to their accounts.

"Individuals locked out of their preferred email inbox due to buggy code are likely to lose confidence in the mail system. But changing email systems is less-than-convenient for the user, so frustration levels can go sky-high," said Gartner analyst Matthew Cain. "I suspect Google will move the bug fix up the priority list as the social media hue and cry grows around this issue."

To reduce the risk of tripping over this issue, Google recommends that people use "a browser other than Firefox" when composing an email with images in its message body. They should also avoid using the "drag and drop" method for inserting large images into messages, and instead add them as attachments by clicking on the paper clip icon.

"We're working hard to resolve this issue," the Google support note reads.