Something in has changed in Snow Leopard that causes problems on some Gmail and Google Apps accounts. I’m not completely sure whats going on behind the scenes, but a problem has arisen where Gmail complains the “Account exceeded bandwidth limits.” This means that too much data has travelled between Mail.app on your Mac and Gmail, and Google automatically cuts your account off to maintain service for other users.

If you’ve already been blocked, don’t worry, you can still get your mail online. The block should be removed within a day. I also changed this setting that seems to have prevented me from getting blocked again. In the menubar, click Mail > Preferences > Accounts > select your account > Advanced and change the “Keep copies of messages for offline viewing” to “All messages, but omit attachments”.

Select "All messages, but omit attachments"

Please tell me if this solution works for you guys. I hope that either or Apple or Google comment on this issues because it does seem to be effecting a number of people.