Mail not responding when syncing with Google Apps Gmail account in OS X Yosemite 10.10.1
I turned off all "Show in IMAP" label settings in the Gmail web console.


I then added back only "All Mail."  I restarted Mail.app and reenabled the account. 
Mail started normally and my email was available.  

I still would like to know the source of the issue, but for now the problem is resolved.