I've recently changed language in my GMail settings, and the folder names have changed (shame on you, GMail!). Therefore, the claws' requests on old folders resulted in 'SELECT ERROR's (I can see them in the log) but no verbose errors. Considering the amount of noise claws makes when it can't connect to the server, e.g. when network is down and you have to click through 5 errors, this is at least disturbing. And since it was a low load mailbox and claws does not notice new folders, I didn't even notice that I'm not getting new mail for almost a week. I think that claws should be more verbose in reporting server errors during mail fetching. Even irritating errors are better than new mail being ignored silently.
You didn't provide a log, but I think this is basically the same as #1641. *** This bug has been marked as a duplicate of bug 1641 ***