Mine has been working fine all day now without any problems, so it must have been one of those things (can't be bothered to switch them around to find out which, don't want it to break again!) Weird because I would have thought the offline viewing setting would have been the more obvious...
I *think* I fixed mine - at least it's working ok now. I had both IMAP and POP enabled in gmail settings - so I disabled POP and it's been fine for the last 30 minutes. I have no clue why that would work though! I also changed the account in Mail to not download all messages for offline viewing...
Mine randomly becomes available but it almost always times out... While it is not working I also cannot log in via the web - I get a message saying my account is temporarily unavailable. This happens on my work computer too (windows).
I'll be following this thread with the hope that someone...