I have similar problem; I have three accounts, one Gmail, one Google apps for domain, and a third one, all using imap.
No problems until the beginning of September (actually Ithink I noticed the error appearing begore a few times, but eventually everything got synced...).
I only have the problem with the Google domain account now -which is a work email, and has to work...
Anyone has a solution for the default email (@) application? Isee several people have been experiencing a problem since August / also browsing some other forums. I epuld not want to install K9 app, though - but if no solution will be available soon I guess I will have to
So if u are aware how to tacle this issue, please share.